Final answer:
Option D, increases in Chinese purchases of U.S. exports, is not a U.S. supply shock; rather, it is a change in demand. Supply shocks, such as a drought or a drop in oil supply, directly affect the market's supply side, unlike increasing demand from foreign buyers.
Step-by-step explanation:
The answer to which one of the following is not a U.S. supply shock is D. Increases in Chinese purchases of U.S. exports. A supply shock refers to a sudden change in the supply of goods or services which can significantly affect the equilibrium in the market.
Supply shocks can be negative, such as a drought or a drop in oil supply, or positive, such as a technological advancement that increases production efficiency. When unions force an increase in wage rates or when there is a reduction in food production due to drought, these can be considered negative supply shocks because they reduce the supply of labor or goods, respectively.
On the other hand, increases in Chinese purchases of U.S. exports do not represent a supply shock but rather a change in demand.
It is an external factor that affects the demand for U.S. goods, potentially raising the quantity sold and the revenue for U.S. exporters, but it does not directly affect the supply side of the U.S. economy.