12.A typical family in the United States in 1900 had a purchasing power equal to the real U.S. GDP per capita in 2015. a. 1 b. 12 c. 70 d. 136 % of 13. Education's effect on productivity: 2. is believed to be less important than the amount of physical capital a worker has available. b. is even more important than increases in physical capital. c. has fallen in the past century in the United States. d. depends on the wealth of the country