Taken together, those three changes lead to a different analysis. Herndon, Ash, and Pollin conclude that “the average real GDP growth rate for countries carrying a public debt-to-GDP ratio of over 90 percent is actually 2.2 percent, not -0.1 percent as as published in Reinhart and Rogoff.”

It’s worth emphasizing, however, that the Excel coding error itself is only responsible for a small portion of this difference in results — about 0.3 percentage points.