Final answer:
By 1990, a significant proportion of the U.S. population resided in the suburbs, following a trend of urbanization and suburban growth that intensified in the post-war era and continued throughout the latter half of the 20th century, culminating in about 80% of the population living in metropolitan areas, including suburbs, by recent times.
Step-by-step explanation:
In 1990, the proportion of the U.S. population residing in suburbs is not directly stated but can be inferred from the fact that by 1960, about one-third of the U.S. population was already living in the suburbs. Given the substantial growth of suburbia in the post-war period and the trend of urbanization, the proportion likely increased beyond the one-third mark. Considering that about 80% of the U.S. population lived in metropolitan areas by recent accounts, which includes suburbs, the suburban population in the 1990s would have represented a significant segment of that figure.
The rapid growth of suburbs in the 1950s and the ongoing urbanization trend that continued throughout the latter half of the 20th century contribute to the understanding that a substantial portion of the U.S. population was living in suburban areas by 1990. Factors such as affordable housing, desire for safer environments, and the pursuit of the American dream contributed to the suburban expansion and continued to attract residents from urban centers.
Data highlighting population shifts from rural to urban settings, especially to suburban areas, further underscores the suburbanization trend, which continued well into the 1990s. Suburban areas became the embodiment of family-oriented, middle-class living, markedly influencing the demographics of the United States.