Kamionka, Thierry; Lacroix, Guy - 2005
applied for welfare between January 1994 and March 1995. It turned out only 3,315 took part in the experiment despite a 50 … external validity of the experiment. We compare the estimated impact of the program using experimental data only to that … obtained using additional data on individuals not taking part in the experiment. We find strong evidence of non-response bias …