This weekend, I published an analysis of the new Boston Marathon qualifying times – and whether they hit certain age groups harder than others.
As I concluded that analysis, I noticed that the distribution of runners in the Boston Marathon and across all marathons in the United States were quite different. The 45-49 age group was the largest group for both men and women at the Boston Marathon.
But when I analyzed the results of all marathon runners in 2024 to calculate the average marathon time, I found the largest age group to be the 25-29 age group for both men and women. I’ve previously looked at the changing demographics of marathon runners, but at the time I was more focused on gender than age.
Now, I’m noticing that there seems to be a trend towards younger runners – among both men and women. As I’ve worked through results for the Boston Marathon Cutoff Tracker, I’ve seen this in a few individual races. For example, there was a huge surge in finishers at Austin – and almost all of them were under 35.
Today, I wanted to take a quick look at the bigger picture – to see what the age distribution of runners in the United States was in 2024 as well as how that changed from 2023 to 2024.
The data we’re using for this is the same data I used to calculate the average marathon times in 2024. It contains races in the United States with 200 or more finishers. There were ~250 races and 400,00 finishes in each year. The results have been deduplicated, and each runner is only represented once (to the extent that this is possible).
Let’s dig in.
What Was the Age Distribution of Runners In 2024?
Let’s start with a look at the current status quo. What was the age distribution of marathon runners last year?
In the visual below, runners are sorted into five year age groups from under 20 to 80+. The counts have been normalized to show the total as a percent of all runners of that gender. The bars on the left show the data for men and the bars on the right show the data for women.
At first glance, the distribution looks fairly similar. There is a peak in the late 20’s and early 30’s, and then things taper off.
But when you look a little closer, there are a few differences.
For both men and women, the 25-29 age group is the largest age group. However, among women it’s quite a bit larger than any other age group. 19.3% of women are 25-29, and the next closest age group is 15.5%. Among men, 16.3% are 25-29, and the next age group is very close at 15.8%.
If women have a spike in one area, there must be an offsetting nadir. And that comes to the right. There are some minor differences among the age groups through 55-59, but the biggest differences are at 60+.
For each age group at the right end of the chart, that age group’s share among women is smaller than that age group’s share among men. If you total them all up, 4.25% of women are 60+ compared to 6.44% of men.
The numbers are small, so the difference may not seem huge. But older men make up about 50% more of the entire male field than older women do of the women’s field.
Is This a Deviation From the Past?
It’s not crazy to think that the largest age groups are the younger ones. After all, it’s quite likely that most runners start running at an early age. Sure, some runners start out in the masters category. But most runners age into it.
Still, this didn’t jive with some data that I’ve looked at in the past.
For example, I analyzed the changing demographics of runners across a cross section of marathons from 2010 to 2019. In that analysis, the 25-29 was the largest among women – but it was basically the same size as the 35-39 age group. And among men, it was nowhere near the top. The 35-39 age group was the largest, followed by the other age groups in the 30’s-40’s. The 25-29 age was much lower, equal in size to the 50-54 age group.
When I explored another sample of runners that extended from 2001 to 2019, the general order of things was similar. For women, the 25-29 age group was at or near the top throughout the entire time period, but it never pulled far away from the others. And for men, it was consistently in fifth place. The only difference over the time period is that in 2001, the 45-49 age group was much smaller – and comparable to 25-29 – before growing over the next twenty years to match the other age 30-40 year old age groups.
And when I looked specifically at the New York City Marathon, the 25-29 age group has never been the largest age group for men. That was the 30-34 age group in the 1970’s, and it shifted over time to the 35-39 / 40-44 age groups. For women, it was the largest age group through the 1970’s, 80’s, and 90’s. But in the 2000’s and 2010’s, it was roughly equal to the 30-34 age group. This trend reversed itself in a big way in 2023, when the 25-29 age group was, by far, the largest.
So in the last twenty years, the average age of marathon runners has shifted up – and the younger, 25-29 age group has been smaller than other age groups. Especially among men.
What Changed From 2023 to 2024?
Those examples are based on samples, and only New York City considers data from post-COVID. So let’s take a look at a huge dataset – all marathons in the United States with more than 200 finishers – and see how things changed from 2023 to 2024.
I’ve broken things out into two visuals – one for women and one for men. In each case, the data for 2023 is on the left and the data for 2024 is on the right. Again, these have been normalized, so the bars add up to 100% – despite the fact that there were significantly more finishers overall in 2024.
To get started, here’s the data for the women.
The overall shape of the graph is similar, but there is a definite shift to the left. The biggest age group – 25-29 – increases from 17.4% to 19.3%. The under 20, 20-24, and 30-34 age groups also increase somewhat.
From 35-39 to the right, each age group makes up a smaller percentage of the overall field in 2024 than in 2023. Relatively speaking, they’re shrinking.
If you were to look at the actual number of finishers, these age groups remained about the same size or increased slightly. But they’ve shrunk relative to the younger age groups because the number of runners in the 25-29 age group increased by almost 30%.
And here’s the same graph for the men. The trend here is the same – towards the left.
There’s also a change in the largest age group. In 2023, the 30-34 age group is slightly larger than the 25-29 age group. This flips in 2024.
But both of those age groups, along with under 20 and 20-24, increase in relative size. Every other age group shrinks in relative size.
Relatively speaking, there are an increasing number of runners under 35 – and a decreasing share of masters runners.
As with the women, the absolute number of finishers increases slightly in most of those age groups. But the number of finishers 25-29 increases by over 30%. There are also huge absolute increases in the other under 35 age groups.
Let’s Put It Altogether
So what does all this mean?
It seems that we are in the middle of a huge surge in participation – specifically among younger runners.
All of the evidence I’ve looked at has shown at least a moderate increase in finishers across the board – including masters age groups. But from 2023 to 2024, there has been a huge jump in runners under 35 among both men and women.
It’s hard to make year over year comparisons before that, because COVID shuffled the deck in 2020, 2021, and 2022. But if you go back to the 2010’s, the relative distribution of runners looks very different.
Among women, things have taken a small shift back towards runners 25-29. Women have always trended more young than men, because women’s running was – for a variety of reasons – restricted in the years of the first running boom. But after years of trending slightly older, they’re reverting towards younger runners.
Among men, things have shifted back towards younger runners in a big way. Men made up the vast majority of the running boom in the 1970’s and 1980’s, and by the 2000’s masters age groups were larger than younger ones. Until recently, the entry of new men into the sport has been slowly declining.
This is a quick and dirty analysis, and I want to come back to this in the future. But it looks to me like the signs of a new running boom.
We’re not just seeing a rebound from COVID – which was what I initially thought when I saw an increase of finishers from 2022 to 2023. We’re seeing a sustained increase, concentrated among younger runners. If these runners stick around for the long term, that points to significant growth in the sport over the next 5 to 10 years as these younger runners age up.
Or, it’s possible these runners only stick around for the short term, run one or two races, and then disappear. I think we’ll have to wait another year or two to see whether this is a sign of true growth or just a short term spike.
Have you noticed an increase in the number of younger runners in your own club and/or races? What do you think about the possibility of a new running boom?