Imagine that in your first job out of college you have been hired as a legislative aide to a congresswoman who is crafting a new antipollution law, intended to be her signature legislative accomplishment. She tasks you with doing historical research on the Clean Air Act of 1970 in order to gain historical perspective on key past legislative efforts. You find that some writers of the period made the interesting argument that the CAA might actually make the air dirtier, since it only covers new plants.

a. What did these writers mean when they made this argument?

b. Other writers support the act, and are unconcerned that this effect would materialize in practice. How would you construct an empirical test to distinguish between these hypotheses?