You are interested in evaluating a program that oﬀers entrepreneurship training to unemployed youth. The non-governmental organization (NGO) implementing the program has compiled a list of unemployed youth who might be interested in the program. To assess the impact of the program, they suggest comparing the incomes of youth who enroll in the training program to the incomes of youth who were not interested in the program. You learn that 50 percent of the unemployed youth on the NGO’s list of potential participants come from poor households; the remainder come from non-poor households. Unemployed youth from poor households are typically unable to ﬁnd even short-term, casual work; so all the poor youth on the NGO’s list are interested in the training program. However, non-poor youth can often earn money doing casual work for their parents or relatives; as a result, only half of the non-poor youth on the NGO’s list are interested in the program.