Which of the following, regarding public finance, is false?

a. U.S. federal tax revenue has been consistently about 20% of GDP since at least

the 1950s, despite large changes in marginal tax rates and economic growth

rates.

b. Public spending tends to be a larger fraction of GDP in more complex, open, and

recent economies.

c. Fiscal stimulus can have an especially large positive effect on the economy

during periods of high unemployment and low aggregate demand.

d. The U.S. debt:GDP ratio declined throughout the 1950s and 1960s largely as a

result of large federal budget surpluses during that period.