Final answer:
Increased government spending after World War II resulted in the growth of the middle class, leading to economic prosperity and improved living standards.
Step-by-step explanation:
The development that most directly resulted from increased government spending in the decades after World War II was the growth of the middle class. With access to well-paying industrial jobs and increased benefits like weekends off and paid vacations, the middle class boomed in the 1950s and 1960s. They were able to use their wartime savings to purchase new automobiles, televisions, household appliances, and suburban homes, which contributed to the overall economic prosperity and rise in the population's standard of living.