A 2018 research paper from the Federal Reserve Bank of Chicago estimates that 60 percent of all U.S. bills and almost 80 percent of all $100 bills are now overseas. That's up from 15 to 30 percent around 1980, according to research from Federal Reserve Board economist Ruth Judson. She found that economic and political instability contribute to this demand.
Projecting future demand for U.S. currency is "challenging" and depends on how quickly the economy grows, interest rates, new payments technologies, and on whether people in other countries continue to see U.S. dollar bills as a useful asset — "all factors that are, to say the least, uncertain," according to the Chicago Fed.
A surge in digital payments may be contributing to the lessening demand for lower denomination bills. Rising smartphone use, a shift toward online shopping and improvements in network bandwidths pushed global digital commerce volume above the $3 trillion mark in 2017, according to a recent McKinsey report. That is on track to more than double by 2022, according to McKinsey.
There has been pressure to get rid of high denomination notes to curb international crime. Lawrence Summers, former Treasury secretary and director of the National Economic Council in the White House, has argued for abolishing $100 bills. Summers wrote an op-ed in The Washington Post in 2016 titled, "It's time to kill the $100 bill."
"A moratorium on printing new high denomination notes would make the world a better place," Summers said, citing its potential for crime. "Here is a step that will represent a global contribution with only the tiniest impact on legitimate commerce or on government budgets. It may not be a free lunch, but it is a very cheap lunch."