ABSTRACT
The economic approach to crime (Becker 1968; Tul lock 1971; Barro 1973; Ehr l ich 1973, 1975; Becker and Landes 1974; Becker and Stigler 1974) develops the concept of a market for criminal activities. The supply of crime is a function o f the costs and benefits of illegal activities and individual risk preference. The demand for crime derives from the free-lunch theorem-not all crime is worth preventing. In
PA = 1 - Pc(1 - PA1c).v - (1 - Pc;)(l - P.wd'. (4) Inserting the behavior of the actors into (4) yields
P_... = 1 - P(D, F, B)[1 - A(N)].v - [1 - P(D, F, B)][l - G(S)]·'", (5)
a;;~ = PnDN[(1 - G).v - (1 - A).v] + NPA.v(l - A)·v-t + N(l - P)GN(1 - G).v-1
- P[(l - A)N In (1 - A)]
- (1 - P)[(1 - G)N In (1 - G)],
(6)
first term in (6). Even i f we could sign the impact of N on police behavior-for example, that more police means better detection and more arrests-the response of criminals would be to commit fewer crimes, and the total effect remains ambiguous. 3 Even if more police reduces the probability that any one policeman will catch a criminal, the larger number of police might lead to an increased probability of detection as N increases. Consequently, it is not possible to say a priori whether more police is associated with more or fewer arrests.4 Since the sign of ∂PA/∂N cannot be determined logically, we seek an empir ical estimate of its sign in the next section.
