How much of a punch did the Federal Reserve’s easy-money policies pack? Quite a wallop, two economists say in a new paper published Friday by the International Monetary Fund.

Former Fed Chairman Ben Bernanke famously quipped in his closing days that the problem with quantitative easing is that “it works in practice but it doesn’t work in theory.”

Not all central bankers and economists have agreed, spurring a debate over the effectiveness of the Fed’s policies. Part of the problem was that it was difficult to determine the impact of bond-buying on borrowing costs.