I have looked at the statistics. I am still getting over 50 visits a day and I have not published much for almost a year. Once I have submitted my thesis I intend to start publishing again. I have a lot to write about.
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Tuesday, 10 January 2012
New Venn diagram for Orison
I have looked at the statistics. I am still getting over 50 visits a day and I have not published much for almost a year. Once I have submitted my thesis I intend to start publishing again. I have a lot to write about.
Wednesday, 8 June 2011
Does the National Statistician understand crime data?
Unsurprising she has recommended that the Office of National Statistics should take responsibility for crime statistics away from the Home Office. This recommendation 5. Recommendation 1 is:
"The body responsible for the publication of crime statistics should seek to improve the presentation of the statistics to give users and the public a clearer understanding of the overall picture of crime, by providing the major and other sources of crime statistics together with additional contextual information."
This will only happen if the statisticians understand the raw data they present. Figure 1 shown above of the report and the explanatory paragraph, clearly shows they do not understand the scope of police incidents. At best the paragraph and figure present a confusing, unclear explanation. In fact it is totally wrong, worryingly wrong, because whoever wrote paragraph and compiled the figure does not have the first clue about the reporting mechanisms resulting in police recorded crime and the contents of the incident database.
The incident database has details of less than 50% of notifiable offences that end up being counted as police recorded crime but contains hundreds of thousands of incidents that come within recorded crime categories that are not counted as police recorded crime. Additionally not all of the 4.3 million notifiable offences are mapped because either they have no mappable location or the fall outside the categorises that are mapped.
Monday, 14 March 2011
What is Geographic Information Science (GISc)?
I am aware that I have not posted for sometime. This is because I have been trying to get my thoughts together to start writing my PhD thesis. I thought I would post part of my introductory section discussing Science and Geographic Information Science (GISc). Without GISc there would be no crime maps so it is quite important. Everything I know about the subject and a lot more is contained in the excellent bestselling book in the world on the subject, that has recently been published in its 3rd edition - "Geographic Information Systems and Science" whose lead author just happens to be one of my supervisors - Professor Paul Longley.
What I am trying to do is explain why GISc is undoubtaby a science (something I needed to be convinced about when I first approached the subject) and to start laying the ground work to justify creating and comparing classifications between areas using crime and policing data.
Science
This section discusses the scientific context of the research. The discussion adopts a simplified approach, guided by others who have studied and written about the nature of science, its definitions and its academic divisions. These processes of definition, simplification, clustering and classification, often in an inexact and overlapping way, are of course central to the scientific method and central to the research carried out in this thesis.
The word ‘science’ is derived from the Latin via Old French and Middle English to denote ‘knowledge’ (Oxford online Dictionary). The purpose of all science is to transform raw data by analysis and/or experimentation into knowledge (Oxford online Dictionary, Longley et al 2010). Knowledge in this sense is an understanding of the system that is being studied so that it can be described by relationships, laws or theories that model its key dynamics. This is a process that goes further than describing a system by providing an insight into how it works. Part and parcel of understanding a system is to be able to identify uncertainties and where possible quantify them; the statistical use of confidence levels of results is an example of this. This quantification of variables and relationships allows research to be reviewed by peers with a view to validation and the generation of new knowledge through further scientific research.
Geographic Information Science (GISc)
The over-arching methodology used by this thesis is Geographic Information Science (GISc). Geography is defined by the (Oxford online Dictionary) as;
“the study of the physical features of the earth and its atmosphere, and of human activity as it affects and is affected by these, including the distribution of populations and resources and political and economic activities.”
The use of the word ‘Information’ refers to the organised collection of data, for instance in a database. GISc relies on Geographic Information Systems (GIS) for the storage of geographic data and organising it so that it can be used for scientific purposes. The data in GIS come from a myriad of different sources, some of which are specific to the creation of mapping the surface of the earth such as satellite imagery and others that are by-products of other data gathering activities such as census data and land-ownership. The data from the disparate data sources are linked by the fact that each row of data in every data set in the system is geo-referenced. This allows the joining of the different data by location or the keeping the data sets separate by layering the data by location or a combination of both. This leads to mentioning the special nature of spatial data that is based on the Tobler’s first law of geography;
“Everything is related to everything else, but near things are more related than distant things” (Tobler 1970).
Tobler’s law refers to spatial autocorrelation which affects the independence of variables which are analysed spatially. This spatial autocorrelation is two dimensional (unlike temporal autocorrelation which is one dimensional) because it radiates out from a fixed point. Both these facts necessitate the use of spatial statistics if the spatial nature of variables is being assessed. The complex nature of the application of Toblar’s Law to crime and policing data is discussed further in this thesis.
The creation of maps is a scientific process, representing the real world is a process of scale selection, data choice and emphasis based on purpose, generalisation and geovisualistion. These methods of representation are by their nature incomplete and imperfect as the only way to perfectly represent the real world is using a 1:1 scale which is pointless and totally impractical. This means that irregular lines on maps, such as coastlines and roads are simplified by excluding the smaller twists and turns; polygon zones are created to show features that are pertinent to the purpose of the map that generalise or amalgamate entities being represented. This can either be completely objective based on measurement and statistical criteria or purely subjective based on the eye of the mapmaker; often it is a combination, this where science meets art. Maps are designed to be intuitive (once the spatial language is understood) by duplicating how human-beings perceive and make sense of the real world both visually and intellectually. Our perception of things goes from the general to the more and more specific as the resolution increases; in a geographical sense, without the aid of maps, this involves travel, for instance moving from seeing a wood in the distance to entering the wood and only being able to see the trees. This raises the question, “Is it better to see the wood or the trees?” The answer is of course “It depends on your purpose.” The conclusion is that, in line with the saying “You cannot see the wood for the trees”, in many circumstances the general can be more important and informative than the specific.
Imperfect clustering and classification are fundamental to GISc. They can be applied to label areas on a map as forests even though there are areas within them of agricultural land or showing the residents of an area as “small town seniors” even though youth offenders are known to live there. The importance of this methodology to this thesis is that it allows hypotheses of relationships between different layers at the same locations to be proposed and comparisons between different locations to be investigated on a single or multi-layer basis. To continue with the tree example, it would be logical to have a polygon denoting timber production on a layer to spatially coincide with a polygon on a separate layer denoting forest but not necessarily all forest polygons spatially coinciding with timber production: If a polygon denoting timber production is nowhere near a forest polygon, this is worth further investigation and explanation.
GISc is a pure science because it is used to empirically measure and represent geographic characteristics and attempts to understand how they interact with each other. It is also an applied science because much of this knowledge is put to practical use, for example Internet crime maps for the public.
What I am trying to do is explain why GISc is undoubtaby a science (something I needed to be convinced about when I first approached the subject) and to start laying the ground work to justify creating and comparing classifications between areas using crime and policing data.
Science
This section discusses the scientific context of the research. The discussion adopts a simplified approach, guided by others who have studied and written about the nature of science, its definitions and its academic divisions. These processes of definition, simplification, clustering and classification, often in an inexact and overlapping way, are of course central to the scientific method and central to the research carried out in this thesis.
The word ‘science’ is derived from the Latin via Old French and Middle English to denote ‘knowledge’ (Oxford online Dictionary). The purpose of all science is to transform raw data by analysis and/or experimentation into knowledge (Oxford online Dictionary, Longley et al 2010). Knowledge in this sense is an understanding of the system that is being studied so that it can be described by relationships, laws or theories that model its key dynamics. This is a process that goes further than describing a system by providing an insight into how it works. Part and parcel of understanding a system is to be able to identify uncertainties and where possible quantify them; the statistical use of confidence levels of results is an example of this. This quantification of variables and relationships allows research to be reviewed by peers with a view to validation and the generation of new knowledge through further scientific research.
Geographic Information Science (GISc)
The over-arching methodology used by this thesis is Geographic Information Science (GISc). Geography is defined by the (Oxford online Dictionary) as;
“the study of the physical features of the earth and its atmosphere, and of human activity as it affects and is affected by these, including the distribution of populations and resources and political and economic activities.”
The use of the word ‘Information’ refers to the organised collection of data, for instance in a database. GISc relies on Geographic Information Systems (GIS) for the storage of geographic data and organising it so that it can be used for scientific purposes. The data in GIS come from a myriad of different sources, some of which are specific to the creation of mapping the surface of the earth such as satellite imagery and others that are by-products of other data gathering activities such as census data and land-ownership. The data from the disparate data sources are linked by the fact that each row of data in every data set in the system is geo-referenced. This allows the joining of the different data by location or the keeping the data sets separate by layering the data by location or a combination of both. This leads to mentioning the special nature of spatial data that is based on the Tobler’s first law of geography;
“Everything is related to everything else, but near things are more related than distant things” (Tobler 1970).
Tobler’s law refers to spatial autocorrelation which affects the independence of variables which are analysed spatially. This spatial autocorrelation is two dimensional (unlike temporal autocorrelation which is one dimensional) because it radiates out from a fixed point. Both these facts necessitate the use of spatial statistics if the spatial nature of variables is being assessed. The complex nature of the application of Toblar’s Law to crime and policing data is discussed further in this thesis.
The creation of maps is a scientific process, representing the real world is a process of scale selection, data choice and emphasis based on purpose, generalisation and geovisualistion. These methods of representation are by their nature incomplete and imperfect as the only way to perfectly represent the real world is using a 1:1 scale which is pointless and totally impractical. This means that irregular lines on maps, such as coastlines and roads are simplified by excluding the smaller twists and turns; polygon zones are created to show features that are pertinent to the purpose of the map that generalise or amalgamate entities being represented. This can either be completely objective based on measurement and statistical criteria or purely subjective based on the eye of the mapmaker; often it is a combination, this where science meets art. Maps are designed to be intuitive (once the spatial language is understood) by duplicating how human-beings perceive and make sense of the real world both visually and intellectually. Our perception of things goes from the general to the more and more specific as the resolution increases; in a geographical sense, without the aid of maps, this involves travel, for instance moving from seeing a wood in the distance to entering the wood and only being able to see the trees. This raises the question, “Is it better to see the wood or the trees?” The answer is of course “It depends on your purpose.” The conclusion is that, in line with the saying “You cannot see the wood for the trees”, in many circumstances the general can be more important and informative than the specific.
Imperfect clustering and classification are fundamental to GISc. They can be applied to label areas on a map as forests even though there are areas within them of agricultural land or showing the residents of an area as “small town seniors” even though youth offenders are known to live there. The importance of this methodology to this thesis is that it allows hypotheses of relationships between different layers at the same locations to be proposed and comparisons between different locations to be investigated on a single or multi-layer basis. To continue with the tree example, it would be logical to have a polygon denoting timber production on a layer to spatially coincide with a polygon on a separate layer denoting forest but not necessarily all forest polygons spatially coinciding with timber production: If a polygon denoting timber production is nowhere near a forest polygon, this is worth further investigation and explanation.
GISc is a pure science because it is used to empirically measure and represent geographic characteristics and attempts to understand how they interact with each other. It is also an applied science because much of this knowledge is put to practical use, for example Internet crime maps for the public.
Saturday, 19 February 2011
Crime Statistics, are the Statisticians to blame for lack of confidence?
Sir Michael Scholar, the UK's National Statistician, pictured above, has been asked by the Home Secretary to carry out a review of crime statistics with the purpose of increasing public confidence in them. He has published a questionaire that can be found here that anyone can complete and submit. Below are my thoughts. I probably have not started off very well by putting some of the blame for low confidence in the crime statistics on the statisticians themselves, but I try to tell it as I see it. Having heard Sir Michael speak at the Royal Statistical Society I am sure he and his staff will be receptive to my views.
It should be the responsibility of a body independent of government but reports to the Home Office in a similar way that the Bank of England is independent of the Treasury but reports to the Chancellor of the Exchequer.
It would a mistake for it to be given to the UK Statistics Authority as I think that one of the major problems that needs to addressed is the fact that it is obvious that the statisticians do not understand the data fully, given its legal and procedural subtleties and have difficulty in producing reports that the policy makers or the public properly understand.
It would a mistake for it to be given to the UK Statistics Authority as I think that one of the major problems that needs to addressed is the fact that it is obvious that the statisticians do not understand the data fully, given its legal and procedural subtleties and have difficulty in producing reports that the policy makers or the public properly understand.
There is far more to crime statistics than just statistics, a major part of it is understanding crime and policing; which are the domains of criminology and police science. With the increasing use of maps to communicate the statistics to the public the discipline of Geographic Information Science is becoming more and more important.
Q2: Is there also a case for transferring responsibility for the management and/or compilation of data collected from the British Crime Survey and the police ? If so, where?
The National Audit Office should be seriously considered for police recorded crime. Even though the data is not financial per se, the skill sets of auditors are very compatible. One of the main challenges to the accuracy and integrity of police recorded crime statistics is that they are used as primary measures of police performance. The procedures for managing and collecting crime statistics to ensure uniformity within and between police forces needs to be overseen by people who have the forensic skills to identify deliberate under recording. As crime reduction and clear-up rates are directly related to individual police officers promotion prospects and pay the auditors should also have sanctions that they can enforce on individuals.
The British Crime Survey (BCS) should be totally independent of the police recorded crime statistics and pressure from the government. It has been a mistake to have one official publication trying to link police recorded crime with the BCS because it makes it look that the two sets of data can be compared directly. In most cases there are reasons why they cannot (due to business and youth crimes not being included for instance) the only notable exception is residential burglaries (but the fact that the BCS uses a rolling 12 month period and the police statistics use a fixed 12 month period affects this and the others crimes). As far more data is collected by the BCS than are published in the resulting dual publication it has the feel that the BCS data is being used to put a political spin on the police recorded crime data. This is at the hub of the need for independence. As important is the long term funding of the BCS so there is not a pressure to please the funding master/mistress to gain continued support.
The linking of different crime data sets should be done independently by academics and those putting them to practical use.
Another solution is to make the two data sets directly comparable which is preferable – see the 4th paragraph of the answer to Q5.
Q3: Currently, the Home Secretary determines what is recorded by the police as a crime and approves the Home Office Counting Rules for crime and statutory data requirements from the police. Should this continue or would public trust in the statistics be enhanced if this responsibility moved elsewhere? If so, where and why?
The Home Office should determine police priorities and ensure that bureaucracy is minimised; these are levers for doing this. The agency managing the collection of the police recorded data, my suggestion the National Audit Office, should be required to comment on whether the rules and requirements properly reflect the level and nature crime in the country.
Crimes in crime statistics always have a legal definition and sometimes in addition a descriptive label. For instance in law there is no offence of burglary dwelling, snatch, armed robbery, it is burglary, theft and robbery (with firearms offences). The labelling in the main allows offences against vehicles to be distinguished and with a bit of delving those offences against people; this should be made clearer. Equally important are those crimes that occurred in a private place or a public place. Under the present labelling it is often not possible to make any inferences in this regard. I think this is vital to understanding the crime problem and police performance.
There are ten Home Office (HO) crime types. The one that leads to the most misunderstanding, confusion and distrust is HO crime type 1 – violence against the person. It is not helped by the fact that statistics that are derived from it are referred as ‘violent crime’ by Home Office publications and politicians. The public order offence of violent disorder (that usually includes violence against the person but not necessarily) which is not included in HO crime type1, shows that violent crime in law applies to criminal damage as well as assaults. This aside, robberies, sexual assaults, aggravated burglaries, kidnapping and arson endangering life which are specifically violence against the person offences are not included in HO crime type 1. The inclusion of common assault (section 39 of the Criminal Justice Act 1988) in the sub-type of ’without injury’ is misleading because there almost always is an injury but not of a permanent nature; only assaults without battery should be included in this sub-type.
If the category of violent crime is important to the public and politicians, which I believe it rightly is, then all crimes that are violent should be included in that category with sub-categories as necessary. If this means double counting of certain crimes because they also meet the criteria of another category, this should not be a problem as long as it is properly explained.
Official Crime Statistics have taken advantage of police computerisation of crime records in the collection of data but not in the scope of what data is collected.
Police accountability and crime prevention would be aided by counts of characteristics (age, gender, ethnicity, geodemographic group for instance) of victims of crime and suspected offenders broken down by crime types and offences. Advances have been made in providing location data about crimes through the medium of maps on the Internet, the accountability and crime prevention advantage could be further enhanced by the provision of data of when (date, day, hour) offences had been committed and/or discovered.
The dark figure of unreported and unrecorded crimes is very important to assessing police performance and confidence in police. I would argue the best proxy measure of confidence in police and police efficiency is the size of that dark figure which is known to vary from offence to offence. The BCS was originally set-up to shed light on this dark figure but as I have mentioned in my answer to Q2 the lack of direct comparability of the two data sets affects the confidence in the accuracy of the estimates produced. A reliable figure can be produced of unreported and reported BCS crimes but the figure for reported and unreported police recorded crime is less reliable. This makes the important figure of those crimes reported to the police but not recorded by the police also unreliable.
The solution to this is not to change the methodology of the BCS but to extract only those crimes that are covered by BCS from the police crime computers for comparison purposes. This is feasible given the data contained within each police crime record and the modern searching power of computers. If the characteristics of victims was also included then very useful assessments of police engagement with different communities would result and provide a good proxy indicator of the level of confidence different communities have in the police. The accurate assessment of the nature of the dark figure for different offences would provide a good measure of police effectiveness and efficiency. This would balance police recorded crime reduction targets that can be achieved through the public feeling that it is not worthwhile reporting crimes to the police.
The Reassurance Gap that led police to realign resources from response policing to neighbourhood policing arose because the public perceived that the crime problem was getting worse even though the official crime figures were showing year on year improvements. The analysis of this included an assessment that one of the reasons for this was that the official crime figures did not match the experiences of people. Drawing on Incivility Theory from the USA and the newly developed Signal Crime Perspective in the UK it is generally agreed that the observable nature of crime and disorder rather than officially collected crime figures influence people’s perception of crime and therefore their level of fear of crime. The all pervasive low level disorder (antisocial behaviour or incivilities) has as much influence, if not more, than the observation of serious crime on people’s perception. Police recorded crime, because of the way it is collected and legally categorised will never be totally in tune with people’s perceptions. My research includes analysing police incident data to see if the data can be used to produce maps that more closely match people’s observations of crime and disorder. The importance of this is that if policy makers and police have a view of the policing problem in a neighbourhood that is not matched by the communities living and frequenting there then there will be a mismatch of priorities and expectations. Research has shown that trust is based on good engagement and communication, crime statistics and maps based on them can either alienate or engage. Police incident data is being used to map anti-social behaviour but it should be used much more widely to reflect the nature and levels of violent crime. Police incident data has the added value of having good temporal attributes and shows details of the police response and priorities, and also the priorities and engagement of the public.
The most important consideration for trustworthy crime statistics is that they are understood. The Home Office Counting rules, legal definitions, Home Office Crime Types, especially in relationship to violent crime are all barriers to proper understanding of police recorded crime. The intricacies of methodology and statistical techniques are barriers to properly understanding, evaluating and therefore trusting the BCS statistics.
The police incident data set is in everyday language, it reflects what people observe and it is easy to explain the origins and validity of the data. It cannot replace the police recorded crime statistics or the BCS but it enables the public to know and understand what the police in their local area are dealing with on a day to day basis. My evaluation of police incident data shows that police recorded crime probably accounts for fewer than 50% of their workload of crime and disorder related. This means that crime statistics would be considerably enhanced as a performance measure if police incident data were included.
The National Audit Office should be seriously considered for police recorded crime. Even though the data is not financial per se, the skill sets of auditors are very compatible. One of the main challenges to the accuracy and integrity of police recorded crime statistics is that they are used as primary measures of police performance. The procedures for managing and collecting crime statistics to ensure uniformity within and between police forces needs to be overseen by people who have the forensic skills to identify deliberate under recording. As crime reduction and clear-up rates are directly related to individual police officers promotion prospects and pay the auditors should also have sanctions that they can enforce on individuals.
The British Crime Survey (BCS) should be totally independent of the police recorded crime statistics and pressure from the government. It has been a mistake to have one official publication trying to link police recorded crime with the BCS because it makes it look that the two sets of data can be compared directly. In most cases there are reasons why they cannot (due to business and youth crimes not being included for instance) the only notable exception is residential burglaries (but the fact that the BCS uses a rolling 12 month period and the police statistics use a fixed 12 month period affects this and the others crimes). As far more data is collected by the BCS than are published in the resulting dual publication it has the feel that the BCS data is being used to put a political spin on the police recorded crime data. This is at the hub of the need for independence. As important is the long term funding of the BCS so there is not a pressure to please the funding master/mistress to gain continued support.
The linking of different crime data sets should be done independently by academics and those putting them to practical use.
Another solution is to make the two data sets directly comparable which is preferable – see the 4th paragraph of the answer to Q5.
Q3: Currently, the Home Secretary determines what is recorded by the police as a crime and approves the Home Office Counting Rules for crime and statutory data requirements from the police. Should this continue or would public trust in the statistics be enhanced if this responsibility moved elsewhere? If so, where and why?
The Home Office should determine police priorities and ensure that bureaucracy is minimised; these are levers for doing this. The agency managing the collection of the police recorded data, my suggestion the National Audit Office, should be required to comment on whether the rules and requirements properly reflect the level and nature crime in the country.
Q4: The Terms of Reference for the review asks for consideration of the current definitions of crime. Do you have any comments?
There are ten Home Office (HO) crime types. The one that leads to the most misunderstanding, confusion and distrust is HO crime type 1 – violence against the person. It is not helped by the fact that statistics that are derived from it are referred as ‘violent crime’ by Home Office publications and politicians. The public order offence of violent disorder (that usually includes violence against the person but not necessarily) which is not included in HO crime type1, shows that violent crime in law applies to criminal damage as well as assaults. This aside, robberies, sexual assaults, aggravated burglaries, kidnapping and arson endangering life which are specifically violence against the person offences are not included in HO crime type 1. The inclusion of common assault (section 39 of the Criminal Justice Act 1988) in the sub-type of ’without injury’ is misleading because there almost always is an injury but not of a permanent nature; only assaults without battery should be included in this sub-type.
If the category of violent crime is important to the public and politicians, which I believe it rightly is, then all crimes that are violent should be included in that category with sub-categories as necessary. If this means double counting of certain crimes because they also meet the criteria of another category, this should not be a problem as long as it is properly explained.
Q5: It has been said that the crime statistics provide a partial picture. What, if any, are the main gaps in Home Office crime statistics that you feel should be addressed as a priority?
Official Crime Statistics have taken advantage of police computerisation of crime records in the collection of data but not in the scope of what data is collected.
Police accountability and crime prevention would be aided by counts of characteristics (age, gender, ethnicity, geodemographic group for instance) of victims of crime and suspected offenders broken down by crime types and offences. Advances have been made in providing location data about crimes through the medium of maps on the Internet, the accountability and crime prevention advantage could be further enhanced by the provision of data of when (date, day, hour) offences had been committed and/or discovered.
The dark figure of unreported and unrecorded crimes is very important to assessing police performance and confidence in police. I would argue the best proxy measure of confidence in police and police efficiency is the size of that dark figure which is known to vary from offence to offence. The BCS was originally set-up to shed light on this dark figure but as I have mentioned in my answer to Q2 the lack of direct comparability of the two data sets affects the confidence in the accuracy of the estimates produced. A reliable figure can be produced of unreported and reported BCS crimes but the figure for reported and unreported police recorded crime is less reliable. This makes the important figure of those crimes reported to the police but not recorded by the police also unreliable.
The solution to this is not to change the methodology of the BCS but to extract only those crimes that are covered by BCS from the police crime computers for comparison purposes. This is feasible given the data contained within each police crime record and the modern searching power of computers. If the characteristics of victims was also included then very useful assessments of police engagement with different communities would result and provide a good proxy indicator of the level of confidence different communities have in the police. The accurate assessment of the nature of the dark figure for different offences would provide a good measure of police effectiveness and efficiency. This would balance police recorded crime reduction targets that can be achieved through the public feeling that it is not worthwhile reporting crimes to the police.
The Reassurance Gap that led police to realign resources from response policing to neighbourhood policing arose because the public perceived that the crime problem was getting worse even though the official crime figures were showing year on year improvements. The analysis of this included an assessment that one of the reasons for this was that the official crime figures did not match the experiences of people. Drawing on Incivility Theory from the USA and the newly developed Signal Crime Perspective in the UK it is generally agreed that the observable nature of crime and disorder rather than officially collected crime figures influence people’s perception of crime and therefore their level of fear of crime. The all pervasive low level disorder (antisocial behaviour or incivilities) has as much influence, if not more, than the observation of serious crime on people’s perception. Police recorded crime, because of the way it is collected and legally categorised will never be totally in tune with people’s perceptions. My research includes analysing police incident data to see if the data can be used to produce maps that more closely match people’s observations of crime and disorder. The importance of this is that if policy makers and police have a view of the policing problem in a neighbourhood that is not matched by the communities living and frequenting there then there will be a mismatch of priorities and expectations. Research has shown that trust is based on good engagement and communication, crime statistics and maps based on them can either alienate or engage. Police incident data is being used to map anti-social behaviour but it should be used much more widely to reflect the nature and levels of violent crime. Police incident data has the added value of having good temporal attributes and shows details of the police response and priorities, and also the priorities and engagement of the public.
Q6: What are the most important considerations for trustworthy crime statistics?
The most important consideration for trustworthy crime statistics is that they are understood. The Home Office Counting rules, legal definitions, Home Office Crime Types, especially in relationship to violent crime are all barriers to proper understanding of police recorded crime. The intricacies of methodology and statistical techniques are barriers to properly understanding, evaluating and therefore trusting the BCS statistics.
The police incident data set is in everyday language, it reflects what people observe and it is easy to explain the origins and validity of the data. It cannot replace the police recorded crime statistics or the BCS but it enables the public to know and understand what the police in their local area are dealing with on a day to day basis. My evaluation of police incident data shows that police recorded crime probably accounts for fewer than 50% of their workload of crime and disorder related. This means that crime statistics would be considerably enhanced as a performance measure if police incident data were included.
Q7: What do you consider to be the main strengths of crime statistics?
The main strength of crime statistics especially when applied to a local level through mapping is that they are extremely popular. This provides an excellent communication and engagement tool that should be used positively and honestly.
Police need to exploit this popularity by including police activity data within their maps to reassure the public and demonstrate their worth to society that is far more than what is revealed in the present crime statistics.
Q8: Do you have any other views you wish to feed into this review?
The spatio-temporal characteristics of offences are extremely important to crime prevention as are the characteristics of victim and offenders for crime prevention and public engagement. This points to an integrated system of maps using police recorded crime, police crime system, police incident management system and BCS as source data. My PhD research involves designing such a system with spatio-temporal clustering and classification at its heart.
Saturday, 12 February 2011
CAD incidents - validation of the k means classification method
This post is really quite interesting if you have following my blog.
I have carried out a simple analysis to test three important aspects of my research;
I carried out a k means classification using those four variables with the 365 days of the year as cases (using raw unstandardised data). I asked for seven groups to see if the k means classification could split the days into the right weekdays.
 |
| London police violent and acqusitive crime incident in 2009 numbers each day |
I have carried out a simple analysis to test three important aspects of my research;
- How good is the SPSS 17 k means classification method
- Does the Metropolitan Police Service CAD data contain rhythms and cycles that reflect the lives of the people of London and the way it is policed.
- What is the best CAD data to use to detect these rhythms and cycles.
I carried out a k means classification using those four variables with the 365 days of the year as cases (using raw unstandardised data). I asked for seven groups to see if the k means classification could split the days into the right weekdays.
I find the result shown in the graph above quite exciting. I hope you can see why. The classification recognises a clear difference between Saturdays and Sundays and week days. The week days have been subdivided in two groups. I have been through all the dates which appear to have allocated to the wrong group and there is a very good explanation for each. For instance each Monday that was allocated to the typically Sunday group (group1) were Bank Holiday Mondays. Every other "misallocation" had a weather or holiday related explanation.
I have tried the classification with standardised data and additional and fewer variables but these four variables appear to me to produce the best results.
So I now have even more confidence in the k means classification method, I am convinced I using a good set of data and I am sure that analysing the variations in violent and acquisitive crime incidents in the context of the police response is worthwhile.
Thursday, 10 February 2011
Wednesday, 9 February 2011
Comparing Crime and Disorder in London and (greater) Birmingham
What I am doing here is creating a classification by adding West Midlands police neighbourhoods (mostly Wards) to the MPS wards. The first map is of the West Midlands police area - Birmingham is in the centre, Coventry to the east and Wolverhampton to the west. I am grateful to Andy Brumwell, from West Midlands police for providing me with the shapefile.
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