One characteristic of a public good is that it is ____________, which means that it is costly or impossible to prevent someone from using the good.

Costs of unemployment include

A) structural unemployment. B) the output lost due to the fact that the economy is not running at full employment. C) reduction in the labor force. D) higher wages.

The true causal effect might not be the same in the population studied and the population of interest because

A) of differences in characteristics of the population B) of geographical differences C) the study is out of date D) all of the above