Economists and social scientists have gathered multitudes of data about Millennials’ tendency to delay the traditional milestones of maturity (starting a career, getting married, buying a home, having kids) in favor of a prolonged adolescence.

But in a new study examining household formation patterns in the US, Pew Research Center has isolated the biggest factor behind the rise in those households without a partner or spouse: “The declining ability of men to earn a salary large enough to sustain a family.”

That’s right. As wages for female workers have risen in recent years, wages for their male peers have stagnated. This in turn has weighed on the household formation rate, because men are more reluctant to marry and start families unless they’re earning above a threshold, which Pew identified as $40,000, the Hill reported.

Instead, analysts said, the decline in both marriage and partnerships “All signs point to the growing fragility of the male wage earner,” said Cheryl Russell, a demographer and editorial director at the New Strategist Press. “The demographic segments most likely to be living without a partner are the ones in which men are struggling the most — young adults, the less educated, Hispanics, and blacks.” “The point at which the average young man becomes ‘marriageable’ appears to be earnings of $40,000 a year or more,” Russell said.

Furthermore, in a sign that divorces haven’t been responsible for the surge in single Americans, Pew says the divorce rate has been stable, or even declining, since the 1980s

Russell pointed to data that shows marriage rates increase for younger Americans in connection with salaries. Fewer than half of men between the ages of 30 and 34 who earn less than $40,000 a year are married. More than half of those who make more than $40,000 a year are married, including two-thirds of those who make between $75,000 and $100,000 a year.

The number of Americas living alone has risen since the financial crisis as the global economy has struggled to return to pre-crisis growth rates. All told, the number of Americans living without a spouse or partner has climbed to 42%, up from 39% in 2007, according to the Pew’s analysis of US Census Bureau figures. For those under the age of 35 years old, 61% live without a spouse or partner, up 5 percentage points from a decade ago.

The higher number of spouseless households comes as the marriage rate declines precipitously. Just half of American adults are married, down from 72% in 1960.

The average American woman gets married just after her 27th birthday, while the average man waits until he is 29.5 years old to marry — significantly higher than the median ages half a century ago.

Lower household formation can ultimately drag on population growth as couples delay having children, and more couples forgo parenting altogether. Given Japan's decades long struggle with stagflation, and its looming demographic crunch, maybe the Federal Reserve could kill two birds with one stone and start handing out helicopter money to men.