The 72-year Presidential Cycle

George Washington, Abraham Lincoln, and Franklin D. Roosevelt are almost universally regarded as the three greatest presidents in the history of the United States. Washington took office in 1789, Lincoln exactly 72 years later in 1861, and Roosevelt 72 years after that in 1933. On this page I look at this apparent coincidence as part of a larger pattern. It appears that the quality of U.S. Presidents follows a 72-year cycle, with each president tending to be of a similar caliber to those who took office 72 and 144 years before him. The correlation between the quality of a given president and that of the president who preceded him in the cycle is statistically significant, with a p-value of 0.01181. That is, we can be 98.819% sure that the correlation is not due to chance alone.

My data are drawn from some of the many surveys of historians and scholars which have been conducted with an eye to ranking the United States Presidents from best to worst. Of the surveys cited by the Wikipedia article on the subject, four of them are suitable for my purpose because they provide ratings rather than mere rankings, telling me not only who is better than whom, but by how much. These four are the Siena Research Institute poll pf 1994, the C-SPAN poll of 1999, and the Wall Street Journal polls of 2000 and 2005. The different polls use different scales, so I have normalized them to a mean of 100 and a standard deviation of 15 — the same scale used for IQ. The table below lists each president with his year of inauguration, the average of the (normalized) scores given him by each of the four polls, and the SD of the four scores. The SD figures are pretty low, indicating that the four polls are in general agreement; the one exception is Ronald Reagan (SD = 7.78), on whom there appears to be no real consensus.

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