The demographic shifts taking place in the U.S. workforce make economic growth of 3 percent on a sustained basis highly unlikely, said David Rubenstein, co-founder and co-chairman of The Carlyle Group.
In a CNBC interview Tuesday from the World Economic Forum in Davos, Switzerland, the private equity billionaire said, "I think we'd be lucky and happy to get close to 3 percent. Somewhere between 2.5 and 2.7 would be very good" on average over the next three or four years.
Many current projections call for at least a 3 percent gross domestic product advance in the fourth quarter of 2017, including CNBC's Rapid Update and Atlanta Federal Reserve's latest GDPNow forecast. The Commerce Department's first look at fourth quarter GDP is scheduled for release on Friday.
President Donald Trump has set sustained growth of 3 percent as its economic target, believing the new GOP tax law and business deregulation efforts will be among the policies that help achieve that goal.
"To think an economy of $20 trillion can grow at 3 percent or 3.5 percent, consistently, I think, is hard to believe," Rubenstein told "Squawk Box," citing labor-force dynamics.
The low U.S. employment rate — which held steady at 4.1 percent for last month — is not enough of a factor, he said. "You don't have that many people in the workforce relative to what we've had historically."
The labor participation rate, the percentage of the civilian population working or actively looking for work, has been on the decline since 2000, hovering around levels last since in 1978, according to the St. Louis Fed.
"I hope I'm wrong. I hope we do grow at a higher rate. But I just don't think we will," he said, noting the population is aging with more baby boomers retiring.