In the four decades from 1860 to 1900, the U.S. population nearly trip

In the four decades from 1860 to 1900, the U.S. population nearly tripled. Real Gross Domestic Product (GDP)

(a) fell by more than the amount by which the population increased.
(b) fell by the same amount by which the population increased.
(c) rose at about the same rate as the population increase.
(d) increased by even more than the population increase.

ANSWER

(d)