Last week I published an excerpt from Probably Overthinking It that showed a long-term decline in homophobic responses to questions in the General Social Survey, starting around 1990 and continuing in the most recent data.

Then I heard from a friend that Gallup published an article just a few weeks ago, with the title “Fewer in U.S. Say Same-Sex Relations Morally Acceptable”.

It features this graph, which shows that after a consistent increase from 2001 to 2022, the percentage of respondents who said same-sex relations are morally acceptable declined from 71% to 64% in 2023.

Looking the whole time series, there are several reasons I don’t think this change reflects an long-term reversal in the population:

1) The variation from year to year is substantial. This year’s drop is bigger than most, but not an outlier. I conjecture that some of the variation from year to year is due to short-term period effects — like whatever people were reading about in the news in the interval before they were surveyed.

2) Even with the drop, the most recent point is not far below the long-term trend.

3) Last year was a record high, so a part of the drop is regression to the mean.

4) A large part of the trend is due to generational replacement, so unless young people die and are replaced by old people, that can’t go into reverse.

5) The other part of the trend is due to changed minds. While it’s possible for that to go into reverse, I start with a strong prior that it will not. In general, the moral circle expands.

Taken together, I would make a substantial bet that next year’s data point will be 3 or more percentage points higher, and I would not be surprised by 7-10.

The Data

Gallup makes it easy to download the data from the article, so I’ll use it to make my argument more quantitative. Here’s the time series.

The responses vary from year to year. Here is the distribution of the differences in percentage points.

Changes of 4 percentage points in either direction are not unusual. This year’s decrease of 7 points is bigger than what we’ve seen in the past, but not by much.

This figure shows the time series again, along with a smooth curve fit by local regression (LOWESS).

Since last year’s point was above the long term trend, we would have expected this year’s point to be lower by about 1 percentage points, just by returning to the trend line.

That leaves 6 points unaccounted for. To get a sense of how unexpected a drop that size is, we can compute the average and standard deviation of the distances from the points to the regression line. The mean is 1.7 points, and the standard deviation is 1.3.

So a two-sigma event is a 4.2 point distance, and a three-sigma event is a 5.4 point distance.

Of the 7-point drop:

• 1 point is what we’d expect from a return to the long-term trend.
• 4-5 points are within the range of random variation we’ve seen from year to year.

Which leaves 1-2 points that could be a genuine period effect.

But I think it’s likely to be short term. As the Gallup article notes, “From a longer-term perspective, Americans’ opinions of most of these issues have trended in a more liberal direction in the 20-plus years Gallup has asked about them.”

And there are two reasons I think they are likely to continue.

One reason is the expansion of the moral circle, an idea proposed by historian William Lecky in 1867. He wrote:

“At one time the benevolent affections embrace merely the family, soon the circle expanding includes first a class, then a nation, then a coalition of nations, then all humanity, and finally, its influence is felt in the dealings of man with the animal world.”

Lecky, A History of European Morals from Augustus to Charlemagne

Historically, the expansion of the moral circle seldom goes in reverse, and never for long.

The other reason is generational replacement. Older people are substantially more likely to think homosexuality is not moral. As they die, they are replaced by younger people who have no problem with it.

The only way for that trend to go in reverse is if a very large, long-term period effect somehow convinces Gen Z and their successors that they were mistaken and — actually — homosexuality is wrong.

I predict that next year’s data point will be substantially higher than this year’s.

Here’s the notebook where I created these plots.