Final answer:
Elmer Davis is critiquing the economic model that requires continuous consumer spending growth, implying that dividends for automobile stocks rely on unrealistic increases in consumption, such as a two-car family being pressured to become a three-car family.
Step-by-step explanation:
Elmer Davis is commenting on the unsustainable nature of economic growth that is dependent on continuous consumer spending and ever-increasing consumption. By suggesting that dividends on automobile stock can only be maintained if a two-car family becomes a three-car family, Davis is highlighting the industry's reliance on perpetual sales growth to sustain profits and shareholder dividends. This implies a need for the creation of consumer demand to an almost artificial degree to continue profit growth. There's an underlying critique of a system that requires such unending expansion, which could lead to overproduction, debt accumulation, and environmental strain.