Major wars are funded by “substantial inflation,” according to a new study published by the National Bureau of Economic Research. The study was authored by Hugh Rockoff, an economics professor at Rutgers University.

“During wars against minor powers, the [United States federal] government was able to fund the war by borrowing and levying taxes,” Rockoff wrote. “In major wars, however, there came a point when further increases in taxes could not be undertaken for administrative or political reasons, and further increases in borrowing could not be undertaken except at higher interest rates; rates that exceeded what was considered fair based on prewar norms. At those moments governments turned to the printing press. The result was substantial inflation.”