John D. Rockefeller Ⅲ sez: "We have all heard[citation needed] about a population problem in the developing nations of Asia, Africa, and Latin America, where death rates have dropped rapidly and populations have exploded. Only recently have we recognized that the United States may have population problems of its own. There are differing views. Some say[who?] that it is a problem of crisis proportions — that the growth of population is responsible for pollution of our air and water, depletion of our natural resources, and a broad array of social ills.[SUBTLE]"
You're talking about the widely known concept called the "demographic transition" and it has slowed, not accelerated, the death of the single-income household in the West because it's more affordable to support smaller families and to start families later in life.
Unfortunately suspect this is the right answer.