How Long is a Republican-Nominated Majority on the Supreme Court Likely to Persist?

Ian Ayres and Kart Kandula

Republican-nominated Justices have continuously held a majority of seats on the Supreme Court for 53 years. Even though Democratic Presidents have won five of the last eight presidential elections, Republican-nominated Justices currently hold six seats on the Court. One reason for the persistence of their majority is the strategic tendency of Justices to retire during periods when Presidents of their nominating party hold office. The persistency impact of strategic retirements can be dampened by death or incapacitation as recently dramatized by the deaths of Justices Ginsburg and Scalia.

To get a rough estimate of how long the current Republican-majority is likely to persist, we ran Monte Carlo simulations to estimate the likely future composition of Justices by making stylized (and contestable) assumptions about the retirement decisions, probability of death, and age of newly confirmed Justices. We estimated the likely longevity of a Republican-nominated majority with different probabilities of Democratic success at winning the White House. If Republican candidates repeatedly win the White House in the future, it should be expected that a Republican majority on the Supreme Court would persist long into the future. Here, we instead focus on the likely longevity of this Supreme Court majority if Democratic presidential candidates have an equal or greater probability of winning the presidency than their Republican counterparts.

The Simulation

We make the following assumptions for simulation purposes:

·       Strategic retirements. A sitting Justice would never retire before serving 18 years or reaching the age of 78, whichever comes first. Thereafter, they would strategically retire as soon as a President of their appointing party is in office.

·       Deaths. Justices who do not retire can also probabilistically leave office by dying with age-contingent death probabilities taken from actuary tables. The actuarial data on age-contingent probability of death was taken from the Human Mortality Database for the United States (https://www.mortality.org/).

·       Replacement Justices. Replacement Justices would take office at the age of 50, which is roughly the confirmation age of Justices Brown Jackson and Coney Barrett.

Under these assumptions, we conduct 10,000 simulations of the composition of the Court over the next 50 years.

Caveats

Our assumed retirement rule is unrealistically stylized in assuming there is a 0% probability that Justices will retire before serving 18 years in office or before reaching the age of 78, and a 100% probability thereafter as soon as a President of their nominating party is in office and 0% probability otherwise. There are counterexamples of all three of these retirement assumptions. In particular, if Justices are less strategic in their retirement decisions, the persistence estimated below will be attenuated. Justices may also have different age-contingent mortality risks than the actuarial numbers on which we relied. If Justices live longer than the general population, that would tend to increase the persistence effects that we estimate. Finally, if the Justices who are confirmed in the future are older than our assumption of 50 years, that would tend to decrease the persistence effects that we estimate. For these reasons, our estimates of persistency can at best give a rough idea of the future.

Our Estimates

The following table summarizes our core results:

The table graphs the probability that a Republican-nominated majority will persist for years into the future under different probabilities of Republican presidential success. As one would expect, the likely longevity of a Republican-nominated majority is higher when the probability of Republican presidential success is higher, and the probability of persistence generally decreases overtime when the probability of Republican presidential success is 50% or lower. 

But the principal lesson of the exercise is to show how dramatically strategic retirement can extend the longevity of a Republican-nominated majority even if future Democratic candidates are substantially more successful at the ballot. For example, even if Democratic candidates have a 70% chance of winning each future presidential contest, it is more likely than not that a Republican-nominated majority will persist for more than 25 years. In other words, even if Democrats somehow complete the Herculean task of winning 5 of the next 7 presidential elections, we might still expect to live under a Supreme Court with a continual Republican-nominated majority. A 30% chance of Republican presidential victory still gives Justices in the majority enough opportunity to strategically retire when their nominating party is in power so as to create pronounced persistence across time. If Republicans more realistically have a 50% chance of winning future presidential elections, then the current Republican majority might persist beyond most of our lifetimes. We end our analysis at 50 years, but with a 50% probability of Republicans winning each presidential election, the probability that a Republican-nominated majority will persist for more than 50 years is 65%.

Countfactual Starting Points

Our approach can more speculatively be applied to what the future might have held if the current Supreme Court instead had a 5-4 Republican-appointed majority. This might have happened if (i) Justice Ginsburg had retired in 2013 after serving 20 years on the court and surviving two bouts of cancer or (ii) Merrick Garland had been confirmed after Justice Scalia’s death. In the following figure, we undertake the same analysis assuming that Justice Ginsburg had retired in 2013 and was replaced in that year by a 50-year-old Justice nominated by President Obama:

As one would expect, the longevity of the Republican-nominated majority is estimated to be less persistent. With a 70% probability of future Democratic presidential victories, the longevity of the Republican-nominated majority is more than halved (from more than 25 years to just 10 years). And with a 50% presidential victory probability, the likelihood that a Republican-nominated majority persists for more than 50 years is reduced from 65% to approximately 54%.

Conclusion

The Supreme Court’s legitimacy turns in part on its being democratically accountable. If a party repeatedly wins the presidency (and to a lesser extent controls the Senate), the judicial views of that party should be reflected on the Court. The democratic accountability deficit is particularly acute now as Republican nominees currently hold 6 of 9 seats, notwithstanding the fact that Democratic Presidents have won the White House in 5 of the last 9 ele
ctions.

With the flurry of cataclysmic decisions on reproductive, firearm, and agency rights that have just been handed down, there is a concern that the newly enlarged and invigorated Republican-nominated majority will be ensconced in power for a substantial period. Our estimates try to quantify exactly how long that period might be.

The strategic retirements that are fostered by our system of lifetime appointments create a dynamic with substantial hysteresis. A Republican-nominated majority has already remained in power for fifty years. Our stylized analysis suggests that irrespective of Democratic presidential success, this majority is likely to persist for decades to come. Indeed, the most likely outcome, if our current nomination/tenure/court-size structure remains in place, is that no one currently admitted to the bar is likely to live to see a day when this majority is displaced.

Code available at https://github.com/kartkand/SCOTUS-Monte-Carlo.