1. In an important 1992 paper, Card and Krueger used difference-in-differences to examine the effects of a New Jersey wage law on employment. They got data on fast-food employment in New Jersey and Pennsylvania, which did not increase its minimum wage.\" a] What is the treatment here? What are the treatment and control groups?\" b) Card and Krueger focused on restaurants near the border between NJ and PA. Why?\" c] Suppose that there are only two time periods. Pennsylvania had employment of 23.33 before and 21.1? after, and New Jersey had 20.44 before and 21.03 after. What is the 'difference-in- differences' number showing the effect of the minimum wage law on employment?\" {1] Now suppose you have data for more than two time periods. Write the regression equation.\" e] Your teacher (and your conscience} say you should check trends in the outcome variable for treatment and control groups before the treatment happens. Why?\" {.I 2. Suppose the MN legislature passes a law providing unemployment benets to people who make less than $20M a year. I want to see how these benets a'ect labor force participation.\" a) Why does this setup work well for regression discontinuity?\" b) What would the treatment and control groups be if I did a discontinuity regression?\" c] In general, what are the advantages of doing a DID or regression discontinuity regression? What are the downsides? I\" 'I