Slow growth in US incomes during the 1970s and 1980s was primarily due to a. slow productivity growth in the US. b. increased competition from Japan. c. increased competition from European countries. d. a rapid decrease in the quantity of money in the economy.

The major factor that affects income and economic growth is productivity, though it is not the only one. Several research studies determined that the average productivity of an American worker during the 1970s decreased specially in industries that were hit hard by the continuous oil and energy crises: pipelines, electronics, auto repair, and oil and gas extraction.

Lower productivity plus high inflation rates and increased foreign competition were the perfect economic storm. there were other periods of economic recession were productivity fell in the same proportion or even higher (late 1980s and early 1990s), but the combination of factors made things worse.

The auto industry was severely hit during those years, and it was never able to recover fully. Back then Honda and Toyota gained huge portions of market share, specially in car sales (not pickups) and even today their cars are the best selling (Camry, Corolla, Accord and Civic) while American manufacturers are only focusing SUVs and pickups. If we set aside Apple, the rest of the large American electronics manufacturers are virtually gone (GE and Motorola are Chinese now).

During the 1970s and early 1980s, American manufacturing suffered a lot.