Suppose a new expanded health care policy was implemented in the state of Arizona in 2015. You have collected two cross sections of health care data from the years 2013 and 2017, for a random set of counties in Arizona. You'd like to analyze the effects of expanded health care for low-income families in Arizona. Suppose for the control group, you use middle-income families that are not impacted by the policy change, and for the treatment group, you use low-income families. In using the basic Difference-in-Differences (DD) setup, you do not have to assume that average health trends are identical for low- income and middle-income families in the absence of the expanded health care policy.

a. True
b. False