USING POLICE ARREST DATA TO ESTIMATE THE NUMBER OF BURGLARS OPERATING IN A SUBURBAN COUNTY

• NCJ Number: 50983
• Author(s): L J RICCIO; R FINKELSTEIN
• Date Published: 1977
• Length: 20 pages
• Sale Source: National Institute of Justice/
• Language: English
• Country: United States of America

Annotation

WILLMER'S MODEL IS USED TO ESTIMATE THE NUMBER OF BURGLARS IN MONTGOMERY COUNTY, MD. IN 1976, AND THE BASIC FORM OF THE MODEL, THE DATA USED, IMPLICATIONS OF RESULTS, AND FLAWS IN THE APPROACH ARE DISCUSSED.

Abstract

IT IS NOTED THAT KNOWLEDGE ABOUT THE EFFECTIVENESS OF CRIME CONTROL IS DEPENDENT UPON THE ACCURATE MEASUREMENT OF KEY VARIABLES. CHARACTERISTICS OF THE CRIMINAL POPULATION IN THE AREAS WHERE CRIME CONTROL STRATEGIES ARE BEING TESTED ARE VARIABLES WHICH HAVE PROVEN DIFFICULT TO MEASURE. THIS STUDY PRESENTS ONE METHOD OF ESTIMATING THE NUMBER OF BURGLARS OPERATING IN A GIVEN LOCALE AT A PARTICULAR TIME--MONTGOMERY COUNTY, MD., 1976. THE MODEL USED, WILLMER'S MODEL, IS BASED ON WHAT IS CALLED AN 'OPPORTUNIST' OR 'MANY TEMPTATION' THEORY OF CRIMINAL BEHAVIOR. IT IS ASSUMED THAT THE CRIMINAL IN ANY GIVEN TIME INTERVAL, IS SUBJECT TO A LARGE NUMBER OF INDEPENDENT TEMPTATIONS OR OPPORTUNITIES AND THAT THE PROBABILITY OF A 'LAPSE' (CRIME COMMITTED BY A GIVEN PERSON) ON ANY PARTICULAR OCCASION IS SMALL, SUCH THAT THE EXPECTED NUMBER OF LAPSES HAS A FINITE LIMIT IN A GIVEN PERIOD OF TIME. THIS ASSUMPTION LEADS TO THE ANALYTICAL RESULT THAT THE PROBABILITY OF A CRIMINAL LAPSING IN ANY GIVEN NUMBER OF TIMES IN A TIME INTERVAL FOLLOWS THE STATISTICAL PROPERTIES OF THE POISSON DISTRIBUTION. SOME OF THE PROBLEMS ASSOCIATED WITH THE USE OF THIS MODEL ARE INDICATED. FOR THE PURPOSES OF EXPLORING THE USE OF THE MODEL, IT IS ASSUMED THAT ARREST DATA ARE A VALID MEANS OF ANALYZING THE CRIMINAL POPULATION AND THAT WILLMER'S ASSUMPTIONS ARE FUNDAMENTALLY CORRECT. THE CALCULATIONS PRESENTED ESTIMATE THAT ALTHOUGH THE POLICE APPREHEND A LARGE SHARE OF THE BURGLAR POPULATION, THE GROUP THEY ARREST ACCOUNTS FOR A LESS THAN PROPORTIONAL SHARE OF THE BURGLARIES. ALTHOUGH IT IS CONSIDERED IMPOSSIBLE TO VALIDATE THE MODEL USED, IT IS BELIEVED THE MATHEMATICS USED ARE A SIGNIFICANT FIRST STEP IN ESTIMATING IMPORTANT NONDIRECTLY MEASUREABLE ASPECTS OF THE CRIMINAL POPULATION. (RCB)