# Prediction

November 9, 2020

• Roe v Wade is wholesale overturned before 2025: 13.5%
• Roe v Wade is partially overturned/weakened before 2025: 31.5%
• Overall: 13.5% + 31.5% = 45%

# Analysis

The key questions are:

• Will SCOTUS have an opportunity to rule on abortion?
• What are the views of the current justices on abortion rights?
• How often has a precedent like Roe v Wade been overturned?
• What will the future views of the court be?
• What are the possible outcomes of a case challenging abortion rights?

## What’s the chance the court will have an opportunity to rule on abortion?

One plausible path to the Supreme Court is that a state’s abortion restrictions are challenged in court by an organization or individual who is harmed by them. To illustrate this, consider the 2019 Alabama abortion ban that seems to clearly violate rights established by Roe v Wade. The law’s real purpose was to act as a vehicle to challenge those rights.1 It was swiftly struck down by a district court after abortion providers sued, but appeals may one day land it in front of the Supreme Court.

This is also how Roe v Wade was challenged and partially overturned in Planned Parenthood v Casey when Planned Parenthood challenged a Pennsylvania abortion law.

A doctor or patient who has been convicted of violating an abortion law could also bring a case, but this seems less likely.

Base rate: In the last 20 years, SCOTUS has ruled on at least 5 abortion cases: Whole Women’s Health, Coakley, Stenberg, Gonzalez, and June Medical Services. Only four of these were on abortion restrictions. Coakley was on the right to protest outside abortion clinics. This gives a base rate of one ruling every 5 years.

There is already one case that could effect Roe v Wade that the court punted on, which may return to the court in the future. Some have speculated that the court was waiting for Amy Cony Barrett to be confirmed before taking the case on. Another theory is that they are waiting until after the election. This article says there are 17 case that are “one step away.”

I think the base rate is probably too low because the recent shift toward a more conservative court will incentivize anti-abortion advocates to bring more cases.

I think there is a 90% chance the court hears a case relevant to Roe v Wade before 2025

## What are the views of the current justices on Roe v Wade?

Below I go through each justice and try to assign a probability that he or she opposes abortion rights. These cases are clearly more nuanced than a one dimensional spectrum from support to oppose, and this overview is very cursory, but I think this exercise at least points in the right direction. My starting point is this chart on the ideological leanings of the court, which I then update with the listed links.

Sotomayor: 40% opposes abortion rights

Kagan: 35% opposes abortion rights.

Gorsuch: 60% opposes abortion rights.

Kavanaugh: 60% Opposes abortion rights.

Barret: 80% Opposes abortion rights, but respects precedent.

Roberts: 55% opposes abortion rights

Thomas: 80% opposes abortion rights

Breyer: 20% opposes abortion rights

Alito: 80% opposes abortion rights

If I treat these as independent events, there’s a 59% chance at least 5 judges with rule against Roe v Wade on a given case.

## How often is a precedent like Roe v Wade overturned?

It has happened at least 300 times as of 2018 or 101 times if you only count constitutional cases. The court rules on 100-150 cases per year.

So overturning precedent is somewhat rare. Most of the constitutional cases happened after 1900, so as a first approximation the base rate might be (101 cases)/(120 years * 100 cases) = 0.84% of cases result in overturning constitutional precedent. Another way of looking at this is as a per year rate. Viewed this way, constitution precedent is overturned on average every 120/101 = 1.2 years. With the recent ideological shift in the court, this rate might increase.

## What will the future views of the court be?

Many liberals are currently concerned about the 6-3 conservative majority of the court, but it’s worth pointing out that the composition of the court will continue to change in the future. Three members of the court are 70 or over (Alito: 70, Breyer: 82, Thomas: 72) and may leave the court soon, either due to death or retirement. If Biden is president (99%) then any retirement or death could shift the court back.

Another thing to consider is democratic control of the senate. If the democrats win the Georgia senate races (25% chance) and gain control of the Senate, there’s a nontrivial chance they will try to expand the court or credibly threaten to expand the court (probably less than 50%, but greater than 10%). This might disincentivize the court from making any radical decisions. If Roe v Wade were overturned, I would expect it to be much more probable that the court would be packed, conditioned on democrats gaining control. There’s also the midterms to consider. If the democrats don’t gain control now and the court overturns Roe v Wade, they may gain control in 2022 and pack the court.

## What are the possible outcomes of a case challenging abortion rights?

My impression is that Supreme Court rulings are often more subtle than they’re made out to be, and often the ruling is fairly narrow. This means that the chance of a wholesale reversal of Roe v Wade is less likely than the court slowly chipping away at the precedent. For example, in Planned Parenthood v Casey, Roe v Wade was overturned in the sense that a trimester framework was replaced with a viability framework. This technically “overturned” part of Roe v Wade, but it’s not clear that this tracks the commonsense meaning of overturned. I think most people envision the right being completely reversed rather than slowly weakened. That said, I suspect it’s more likely that Roe v Wade is chipped away at rather than wholesale overturned given the importance that the court assigns to precedence and narrow rulings.

# Putting it together

A first pass at putting this together is taking the 90% chance abortion rights are challenged and multiplying it with the 59% chance the court rules to overturn or weaken those rights. That gives a 53% chance of Roe v Wade being overturned or weakened.

There are a few adjustments I want to make to this. First, the threat of court packing decreases the 59% chance, but not by much. It looks likely the democrats will have to wait until the midterms before they can credibly threaten to pack the courts and even then it’s not a sure thing. Second, the 59% chance of overturning was for a single case. Multiple cases brought before the court increase the chance that at least one challenge will succeed. That said, I don’t think it increases it by much because the outcomes will be heavily correlated. So this increases the 59% by only a little. I think these two adjustments are basically a wash. Finally, I adjust downward due to the low base rate of constitutional precedent being overturned. I end up at a 50% chance of Roe v Wade being overturned or weakened (conditioned on being challenged).

I express this in a yaml based format I developed to express probability trees:

roe v wade is challenged [0.9]:
overturned [0.50]:
wholesale overturned [0.3]: true
weakened [0.7]: true
~overturned [0.5]: false
~roe v wade is challenged [0.1]: false

Which yields the following paths:

[0.1350] roe v wade is challenged {p=0.9} → overturned {p=0.50} → wholesale overturned {p=0.3}
[0.3150] roe v wade is challenged {p=0.9} → overturned {p=0.50} → weakened {p=0.7}

Overall: 0.4500

The adjustments could also be expressed in the tree itself, but that leads to a very complicated tree. When I tried to do this, I ended up with the same ballpark probability (40%-50%).

It’s worth comparing this prediction to a Metaculus question which gives only a 25% chance of Roe v Wade being overturned. I think one reason I’m far from the community forecast is that the resolution criteria for that question are narrow, so it might resolve negative even if Roe v Wade is weakened in some way. That said, it doesn’t resolve until 2028 so it has a much longer time horizon, which should raise the probability. One thing I’m surprised about is that the Amy Barrett confirmation didn’t seem to change the probability much. Maybe forecasters haven’t updated yet. It’s also possible they’re weighing the low base rate much more heavily.

1. “The bill’s sponsor, Republican representative Terri Collins, has stated that she hopes the law will lead to a legal challenge in which Roe v. Wade is overturned.” Wikipedia contributors. (2020, October 22). Human Life Protection Act. In Wikipedia, The Free Encyclopedia. Retrieved 03:28, November 9, 2020, from https://en.wikipedia.org/w/index.php?title=Human_Life_Protection_Act&oldid=984841661↩︎