One occasionally hears that the upcoming election is especially important because the incoming President may have to fill umpty-leven vacancies on the Supreme Court. To remove this jackpot effect, I had the idea of letting the President appoint one member to the Court during each term of Congress, irrespective of vacancies. The size of the Court would thus fluctuate; but how much?
It so happens that there have been 110 such appointments, and the present Congress is the 110th! So I worked out what the numbers would be if the same Justices had been appointed in the same order, one at a time on March 4 of odd-numbered years (when the terms of the President and Congress began until Amendment XX), and resigned or died when they did in real history.
There are some anomalies, of course: thirteen Justices left the Court before I have them appointed (J.Rutledge in 1791, T.Johnson in 1793, Ellsworth in 1800, Moore in 1804, Sanford in 1930, Cardozo in 1938, Byrnes in 1942, W.B.Rutledge in 1949, Vinson in 1953, Minton in 1956, Whittaker in 1962, Goldberg in 1965, Fortas in 1969).
Thus the number reaches -2 in 1800, and does not consistently stay above zero until 1813. It peaks at 10 in 1857, 1859, 1861, 1879, 1887; then declines again, reaching 3 in 1922 and 1925; rises to 7 in 1937; falls to 1 in 1942, 1946, 1949, 1954, 1956; zero in 1957, 1958, 1962, 1969; goes negative in 1971; peaks at 8 in 2005; and is now 7.
In real life, the Court was created with six seats in 1789; expanded to seven in 1807, to nine in 1837, and to ten in 1863; cut back to eight in 1866; and expanded for the last time to nine in 1869.