单选题 The idea behind the Laffer curve is that increases in tax rates do not increase tax revenues proportionately because they decrease the:

A. demand for labor.
B. supply of labor.
C. productivity of labor.

【正确答案】 B

【答案解析】The Laffer curve is based on the concept that income tax rates affect potential GDP because of their influence on the supply of labor. Hence, the name "supply-side" economics.