Introduction

A strange political trend is found in the fact that Democrats — who are overwhelmingly favored by younger voters — tend to elect older Congresspeople. At the start of the 115th Congress in 2017, the average Democratic Congressperson was 60, while the average Republican Congressperson was 55.7. The gap between the medians was even larger: 62 for Democrats vs. 56 for Republicans.

Much of this has to do with the recent electoral success of Republicans. Bringing more new faces to Congress tends to yield a younger caucus overall. Matthew McConaughey put it best: incumbents get older, but freshmen stay the same age.

Republicans had a wildly successful election in 2010 and another successful one in 2014, while their losses in the subsequent presidential years were limited. Of 217 Congresspeople, serving at the start of the Trump presidency, who were first elected in one of the 2010-2016 regular elections, 140 (65%) were Republicans. Many of these are young conservatives swept into power by the backlash against President Obama — folks like Justin Amash (38), Carlos Curbelo (38), and Elise Stefanik (34).

Democrats now stand to make their biggest gains in Congress since at least 2008. I was curious what this would mean for the age distribution of Democrats in the House. The answer: the Congressional age gap is set to narrow, but unlikely to disappear.

Dataset

An existing dataset from Daily Kos provides birth years for all incumbent Congresspeople. To compute expectations for the next Congress, I supplemented this dataset with data from the Prognosticator Tracker, which aggregates election ratings across the three big election handicappers (Cook Political Report, Inside Elections, Sabato’s Crystal Ball). Probabilities of Democratic or Republican victory in each seat are estimated by computing historical averages and then averaging across the three raters.

Candidate birth years had to be manually sourced. Much of this work was done using ages listed in news articles, meaning there are likely many off-by-one errors. The data can be found here — let me know if you spot any issues!

Results

Expectation

In the next Congress, the average Democrat is expected to be about 2.5 years older than the average Republican, a decline from the 4.3 year gap at the start of 2017.

The drop is mostly driven by a crop of younger Democratic candidates in competitive races: the average Democrat is expected to be 58.7 years old at the start of 2019, 1.3 years younger than the caucus average at the start of the current Congress. The average Republican will be 56.2, a slight uptick relative to the current Congress.

As always, I should emphasize that this is an expectation, not a projection. There is a wide range of ages among Democratic candidates in Toss-Up races, from 77-year-old Donna Shalala in FL-27 to 31-year-old Katie Hill in CA-25. If things break disproportionately toward the older or the younger crop, the average Democrat’s age could shift around.

Uncertainty

This brings me to the next point: what we’d really like is a confidence interval. This would be straightforward to compute if the race outcomes were independent, but as I talked about in the last post, they’re not. Covariance between the races can have a big effect on the overall uncertainty. And the covariance matrix is tough to estimate empirically (though FiveThirtyEight seems to have found a way to estimate it).

Even absent a confidence interval, I’ll argue that it’s quite unlikely for the age gap to go away. To see why, note that only 107 races are rated competitive by any of Cook, Gonzales, or Sabato. That means that three out of four races are more or less decided, barring an unexpected event. And here is the breakdown of those seats:

Number of Seats Average Age

(as of 1/1/2019) Safe Democratic 183 61.0 (D) Safe Republican 143 56.7 (R) Competitive 107 47.9 (D)

54.7 (R)

Among the safe seats, future Democratic Congresspeople are a full half-decade older than their Republican counterparts. So to overcome the age gap, Democrats have to both win a lot of these competitive seats (where their average win probability is 36%) and have their wins favor younger Democrats (even though there is zero correlation between Dem win probability and candidate age).

There are configurations where it is possible, but they are exceedingly unlikely.

Next Time

I hope to explore why Democrats aren’t yet electing lawmakers younger than the Republican average.

One intriguing hypothesis is that gender may play a role. In a wide variety of professional settings, biases lead women to be judged as less competent than men. As a result, many often wait to garner more experience before seeking elected office. A consequence is that female lawmakers tend to be older than male lawmakers: the average Congresswoman is about three years older than the average Congressman, for example.

Now, women are on the cusp of major gains in the House. And 78% of the 233 women nominated for Congress are Democrats. So it’s possible that part of the story is about a cohort of mid- and late-career professional women, galvanized by Trump to cast aside doubts and finally throw their hats in the ring.

I’ll aim to explore this theory, and others, in a follow-up piece.