(1)The use of sample selection correction procedures such as the Heckman correction (Heckman 1979) can account for cases' participation decisions. Estimates obtained using these procedures may be sensitive to underlying statistical assumptions, however, and usually are less precise than ordinary least squares estimates.
(2)Sometimes, however, there will be no such correspondence between entry and exit effects, since certain policies (for example, diversion payments or some AFDC-UP expansions) will not apply to current welfare recipients but only to new applicants.
(3)The study of entry effects is separate from the rest of the evaluation. It is being conducted by Professor Michael Wiseman at the University of Wisconsin.
(4)"Manpower Demonstration Research Corporation (1994). Proposal Design and Workplan for Evaluating the Minnesota Family Investment Program. New York: MDRC, p. 28.
(5)If the study also wanted to look at the direct effect of JOBS participation on labor market outcomes, experimental status could be used in a two-staged least squares procedure to predict JOBS participation.
(6)"Werner, Alan, and Robert Kornfeld (1996). "The Evaluation of To Strengthen Michigan Families: Fourth Annual Report: Third Year Impacts." Cambridge, MA: Abt Associates, Inc., p. B-1.
(7)Werner and Kornfeld (1996), p. A-4.
(8)"Knox, Virginia, et al. (1995). "MFIP: An Early Report on Minnesota's Approach to Welfare Reform." New York: MDRC, pp. 4-9.