The world’s richest nations are borrowing for free.

Taken together, the average 10-year bond yield of the U.S., Japan, and Germany has dropped below 1 percent for the first time ever, according to Steven Englander, global head of G-10 foreign-exchange strategy at Citigroup Inc.

That’s not good news. The rock-bottom rates, which fall below zero when inflation is taken into account, show “that investors think we are going nowhere for a long time,” Englander wrote in a report yesterday.

If the global economy was picking up, then bond yields would reflect expectations that inflation would accelerate and riskier assets would prove more attractive. Instead, inflation is on the slide. JPMorgan Chase & Co. forecasts a global rate as low as 1 percent if oil remains below $60 a barrel.

Even during the Great Depression, governments in the U.S. and abroad paid more than now to borrow for a decade, Englander says. At the end of the crisis-roiled 2008, the so-called Group of Three’s rate was still above 2 percent.

More broadly, bonds in the Bank of America Merrill Lynch Global Broad Market Sovereign Plus Index had an effective yield of 1.28 percent as of yesterday, the all-time low, based on data starting in 1996.

The former Federal Reserve Bank of New York economist sees two possible reasons for the free money.

First, it could be secular stagnation, a term popularized by former U.S. Treasury Secretary Lawrence Summers. He contends that rich nations are suffering a persistent lack of demand and should take advantage of the low bond yields to boost spending.

Even with the U.S. accelerating, the world economy is not “out of the woods,” Summers told a weekend conference of economists in Boston.

Englander’s second theory is that while central bankers have been aggressive in cutting interest rates and pursuing quantitative easing, investors may be concluding that policy needs to be even more innovative if it is to gain traction.

It is “striking that this is not happening during the panic phase of a crisis, but after the panic is over and we have had significant recoveries in asset prices globally,” Englander wrote.

Copyright 2018 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.