Middle-class Americans are now outnumbered by those above and below them and are "falling behind financially," according to a new analysis of government data by the Pew Research Center.
The beginning of 2015 saw 120.8 million adults living in middle-income homes, compared with 121.3 million Americans living in lower- and upper-income households, a significant shift that "could signal a tipping point."
According to Pew's report, the 21st century has seen "middle-income Americans" fall behind financially. The median income of middle-income households fell by 4 percent between 2000 and 2014, while median wealth — assets minus debts — fell by 28 percent between 2001 and 2013.
The shift has already spurred a range of calls to action across the political spectrum, and governments may face "a lot of pressure to act" and boost income, said Gary Shilling, president of economic research firm A. Gary Shilling and Co. He told CNBC's "Closing Bell" that it may take shape in fiscal stimulus rather than the monetary stimulus central banks have recently deployed.