Suppose that the supply of fossil fuels like coal and petroleum will become more and more scarce in the next fifty years. With a growing global demand for energy and the looming threat of rising global temperatures, it would seem to be a recipe for a dramatic decrease in the growth rate of economic activity. Why do many economists believe that economies can continue to grow even in the face of resource scarcity? Some economists argue that the official unemployment rate understates the true level of unemployment. Summarize these arguments.