There have been many frauds of historic proportions — for example, the financial pyramid scheme for which Charles Ponzi was sent to prison in the 1920s, and for which Franklin D. Roosevelt was praised in the 1930s, when he called it Social Security. In our own times, Bernie Madoff’s hoax has made headlines.

But the biggest hoax of the past two generations is still going strong — namely, the hoax that statistical differences in outcomes for different groups are due to the way other people treat those groups.