In the three and a half decades after World War II, interest rates in the developed world were on average below zero after adjusting for inflation, according to Carmen M. Reinhart, a professor at the Kennedy School of Government at Harvard. This helped Europe, the United States and Japan slowly whittle away much of their war debt as their economies grew faster than their debt burden.

“The difference is that the postwar period was one of strong growth, when rebuilding and capital investment was going on across the Continent, and there were strong demographics,” said Stefan Hofrichter, the chief economist at Allianz Global Investors. “But these elements are not necessarily in place today.”

For that reason, economists are less certain that the success of the strategy will be repeated.

Many major economies are already slowing down, if not outright contracting. And the actions taken by governments to keep interest rates low can restrain how much savers have to spend and force fragile banks and pension funds to take on more risk. Ultimately, it could crowd out private borrowing.

Governments have different mechanisms to keep their borrowing costs artificially low.

The Chinese government can just make a call to banks and dictate how much they will lend and at what interest rate.

“By forcing them to lend at low interest rates, China’s central bank is taxing banks at high rates,” said Nicholas R. Lardy, a senior fellow at the Peterson Institute for International Economics. “They make it up to the banks by dictating that banks pay depositors even lower rates, so consumers are getting taxed too.”

Inflation-adjusted interest rates on one-year deposits have been below zero since late 2003, he said. China tightly controls how much money can leave the country, so individuals cannot seek higher yields elsewhere. As a result, Chinese families have been investing their growing incomes in real estate, which has led to a huge real estate bubble in some Chinese cities.

Democracies use more roundabout techniques.

“They have to work with their captive audiences — the pension funds, domestic insurance policies, banks, any domestic buyers they can find — to force-feed sovereign debt, sometimes under the euphemism of ‘macroprudential regulation,’ ” said Professor Reinhart.