Which of the following has been shown to be true in the United States about changes in the minimum wage rate?
a. Because a large percentage of the US population receives the minimum wage rate, changes in the rate tend to greatly impact the demand for low-skilled workers.
b. Changes in the minimum wage have historically had a small impact on employment.
c. Changes in the minimum wage always have had some effect on employment.
d. Changes in the rate tend to greatly impact the demand for high-skilled workers.