Reconciliation of Crime Statistics from Different Sources
In an effort to clarify why differences exist in the various data sources from which crime statistics can be obtained, an examination was made of the official Department record called the "Green Sheet" (i.e., "Summary of Crime for the Month of December,..."), the OSR (Offense Statistical Record) file, the Direct Entry System, RAMS (the crime analysis Records Analysis and Management System) and the daily Chief of Police Crime Summary. Each of these data sources is dependent upon the data entered into the mainframe computer whenever a crime report is received from an officer or from the Expediter Unit. Thus, it would seem that the crime statistics generated from these data sources should be nearly identical or at least have no major discrepancies. An examination of these sources, however, reveals distinguishing features that contribute to the differences found in the crime statistics derived from each source. The following is a brief review of each data source and its relationship to the others.
The "Greensheet" is produced from a report titled "Return A" which comes from an Equipment Communications and Information Services Department (ECI) computer program written to incorporate the Federal Bureau of Investigation's Uniform Crime Reporting specification. "Return A" is in turn compiled from other programs which produce periodic reports (e.g., the "Crime Edit Report" and the "No. 1 Crime Summary") that are monitored during any given month by the UCR Unit of the Communications Division. When errors in crime classification, data entry, offense status, etc., are identified by the UCR Unit Staff, the corrections are entered into the computer and the above reports are regenerated later in the month to capture errors in subsequently reported offenses. Finally, at the end of the first week of the following month, the cutoff date for corrections is reached and the "Green Sheet" is produced. Further corrections to that month's crime statistics are made to the crime statistics of the succeeding months. This is done to avoid having to go back and issue corrections to crime statistics already released in previous months.
The programs that produce the data for the"Greensheet" (i.e., the "Crime Edit Report" and the "No. 1 Crime Summary") are generated from the OSR or Offense Statistical Record File. The OSR file is an on-line file that contains basic information about each crime that has occurred during the most recent thirteen month period. Information such as the date and time of occurrence, the address of the incident, the complainant's name, race, sex and age, the type of crime, the status of the crime, the badge number of the officer who made the crime report, the badge number of the investigator assigned to follow-up the case and the type of property taken (if any) is contained in this file. A second on-line file, the Supplemental Statistical Record or SSR File, contains supplemental statistics such as property and crime status information. It updates the corresponding information in the OSR File whenever appropriate.
The OSR file is the source of the crime statistics available on the RBEAT and RCITY review accessed on the mainframe terminals throughout the Department. Since the OSR file is an on-line file, it is dynamically updated as soon as a record is added (or deleted) or a change is made to an existing record. Consequently, the same crime statistics obtained through RCITY and RBEAT one moment may differ one week, one day and even one minute later. In addition, crime counts from RBEAT and RCITY utilize the date that a crime is reported and not the date that a crime is committed. This is consistent with the "Greensheet" but may differ from SAS or RAMS generated crime statistics as will be explained below.
The OSR file is, in turn, generated from the Direct Entry System. A record in the Direct Entry System or DE System is initiated when an officer enters an MDT record or calls the incident in to a Direct Entry operator who enters the report into the mainframe computer or when a record is entered from the Expeditor Unit. When the Staff Review Unit completes its examination of any newly entered DE record and all the corrections are satisfactorily completed, it becomes a record in the DE System. An OSR record is also created at this time from selected information in the Direct Entry System. The DE System consists of many files each holding different kinds of information. The Direct Entry Base File and Investigative Supplement File contain the crime classification information that is transferred to the OSR file.
The data in the RAMS database used by crime analysts is also based upon data from the DE System. Selected data is pulled from the DE System and placed in a temporary mainframe computer file that is downloaded each day into RAMS. RAMS is a microcomputer based application that stores and manipulates mainframe derived data. Since RAMS is updated daily, the offense records it contains may be updated each day. An offense could be deleted of have its crime category classification changed from one day to the next. Then as in the RBEAT and RCITY instances above, crime counts for the same date period may differ depending on the day that each count was made. Another difference in comparing crime statistics results from the extent to which those statistics are to be utilized. The crime analysts utilizing RAMS are most often interested in the date that an offense occurred rather than when the offense was reported. This is essential in detecting crime patterns or providing summaries for patrol or tactical operations. Depending on the situation, an entire day or days could elapse between the time when an offense occurred and when it was reported to the police. Therefore, unless specifically stated otherwise, the crime statistics generated through RAMS reflect the date(s) of occurrence, This becomes a problem when a request is made for crime figures for a given date or date period. Is the date or date period requested referring to the date(s) that the crimes occurred or the date(s) that the crimes were reported? Since most people are unaware of any distinction in the above date categories, they most often mean the date(s) that the crime occurred. A problem will then occur when those figures are compared to the "Greensheet" or RBEAT or RCITY generated statistics that all utilize the reported date.
SAS generated printouts will have the same difficulties as RAMS derived data in comparison with "Greensheet" or RBEAT/RCITY derived data. SAS programs access OSR or Direct Entry file data. Consequently, if the same program is run on two different days, results may differ because files have been updated. The "Chief of Police Morning Report" is a SAS program that has been written to match as closely as possible RBEAT/RCITY data. It does utilize the dates that crimes were reported instead of the dates that crimes occurred. However, it will not match RBEAT or RCITY data that is accessed on a different date than when the "Morning Report" was generated. The "Morning Report" will never match the "Greensheet" since the "Greensheet" is generated several days after the "Morning Report" is run for a specific date period.
In summary, the "Greensheet" is generated from a complex series of special programs written in ECI to comply with the FBI's Uniform Crime Reporting specifications. It is generated several days after the end of each month to capture as many changes to that month's data as is reasonably possible. Other crime data sources utilize different criteria relative to specific needs (e.g., crime analysis, daily or up-to-the-minute crime summaries for administrative or operational purposes, etc.) and therefore should not be compared to the "Greensheet" or to each other.