If I remember correctly, this wasn't really a "mathematics" mistake. The formula simply wasn't applied to the right number of cells (they didn't apply the cell-

If I remember correctly, this wasn't really a "mathematics" mistake. The formula simply wasn't applied to the right number of cells (they didn't apply the cell-selection far enough). Although that's beside the point. This was a tragedy of the academic economist profession, and should be covered day-one in any Econ research class.