The Value of a Young Justice

There are really two questions you can ask about a Supreme Court justice. One is the president’s POV question “is this person the best person in all the world to fill the seat?” and the other is congress’ question “is this person so unacceptable I’ll vote ‘no.’” For the vast majority of progressives, Elana Kagan is going to easily clear the second bar. But that still leaves open the issue of whether it wouldn’t have been better to pick someone with a clear liberal record. Nate Silver constructs a macabre little model to illustrate the fact that Kagan’s relative youth is pretty important:

Wood’s [Value Over Replacement Justice], we’ll assume, begins at 50, since we’re supposing that she’ll side with the liberals 100 percent of the time rather than 50 percent for her replacement. Kagan’s starts at 40: the 90 percent of the time we’ve supposed she’d vote with the liberals, less the 50 percent baseline.

As we go out into the future, however, the Justices become less valuable as they are less likely to survive. For instance, Wood has about an 18 percent chance of no longer being with us 15 years hence, so we’d have to subtract that fraction from her VORJ.

After about 20 years, Kagan overtakes Wood even though she’s less liberal, because she’s more likely have survived. She continues to provide excess value over Kagan from that point forward, until we reach a period 40+ years out where both women are almost certain to be dead. On balance, Kagan’s lifetime expected VORJ is actually higher than that of Kagan’s (1,280 rather than 1,206, if you care), assuming that she’ll defect from the liberals 10 percent of the time whereas Wood never will.

I think this model clearly has too many arbitrary numbers in it to be of actual use in evaluating Kagan vs Wood. But as good models do, it does illustrate the general structure of the situation—notably the fact that life expectancy is of huge importance. That, I think, further underscores the desirability of creating fixed terms for justices. Until then, though, I would encourage progressive presidents to keep appointing women to the high court—they live longer.