The 2024 Chicago Marathon: Three Interesting Data Insights (Plus More)

Last weekend was the the 2024 Chicago Marathon. Over 52,000 runners hit the streets of Chicago for the race.

As I do after each World Marathon Major, I’ve collected the results and analyzed them to see if there are any interesting tidbits. I’ve published a detailed analysis in Runner’s Life, which you can find here.

If you’re not a Medium subscriber, you can request a special link to that article here.

If you’re interested in the other races, here are write ups about this year’s Berlin Marathon, London Marathon, and Boston Marathon.

In the meantime, keep reading below for a brief version of that analysis, along with three visuals and a couple of insights.

If you’ve been reading anything about the Chicago Marathon, you know that Ruth Chepngetich smashed the women’s world record with a mind-blowing time of 2:09:56. The Chicago Marathon is now home to both the men’s and women’s world records. There’s been plenty of press coverage of that – so I’ll be pulling at some other strings.

Specifically, we’ll look at:

1. The distribution of age and gender, and how it varies by American and international runners
2. The distribution of negative and positive splits
3. The number of runners who qualified for Boston

Let’s dive in.

Are Age and Gender Distributed Differently Between American and International Runners?

I’ve been looking at the gender distribution of runners a lot lately.

On the one hand, I’ve noticed that the balance of men and women at American races is becoming increasingly equal. Among younger runners, especially, the historical discrepancies are starting to disappear.

But when I’ve isolated international runners, that’s not the case. At both Berlin and Boston, I’ve noticed that international runners tilt more heavily male than American runners.

That is true of the 2024 Chicago Marathon, as well.

This visual shows the distribution of men (green) and women (orange) along different age groups. The top visual is runners from the United States and the bottom visual is everyone else.

Among American runners, women make up a huge majority of younger runners – and a small majority of runners through their 40’s. Even among older runners 50+, there’s no much difference between the number of men and women.

But among international runners, it’s a very different story. There are far more men than women in almost every age group.

I was also struck by the age difference here. I suppose some of this may be driven by cost – with older runners more likely to have the disposable income for international travel. But it’s still a bit surprising just how much older these international runners are than American runners.

Check out the full analysis on Medium for a more in depth look at the demographics.

How Many Runners Manage a Negative Split?

This was an interesting question, and I figured Chicago was as good a place as any to explore it.

In a perfect world, you want to start your race conservatively and speed up slightly towards the end. Or at least hold on and run roughly the same pace in the second half. But quite often, runners tend to go out too fast early on, suffer in the end, and slow down. Sometimes drastically.

Chicago is a flat course, and it’s full of fast, experienced runners. So how many of them managed to run a “perfect” race?

About 12% – or ~6,000 of 52,000 finishers.

This visual shows the distribution of runners by how much they negative or positive split the race.

This is calculated by taking the difference between their first half and second half splits, and then dividing that difference by the first half. So if a runner took 1:30 (90 minutes) to run the first half and they took 1:35 (95) minutes to run the second half, that’s a difference of 5 minutes. 5 minutes, divided by 90 minutes, is a 5.55% positive split.

On the left side of the graph, there are a few people who have deep negative splits. But the largest group of negative splitters – just over half of them – was between 0 and 2% faster in the back half of the race.

There’s a larger group of ~4,700 runners who ran a slight positive split (0-2%). This is still pretty good pacing.

The largest group ran a 2-4% positive split. From there, the number of runners in each bin gets increasingly smaller. Nonetheless, there is a very long tale – with almost 10,000 finishers slowing down by more than 20%.

For more details – including how the rate of negative splitting varied by age and gender – check out the full analysis on Medium.

How Many People Qualified For Boston?

One final question that I’m sure a lot of people are interested in is how many of these finishers qualified for Boston.

There were a record number of applicants to Boston this year, causing a high cut off time. The BAA reduced the qualifying times for 2026 in an effort to bring that cut off time down to earth.

The Chicago Marathon is one of the largest sources of qualifiers for Boston each year – so the number of qualifiers coming out of Chicago is an important variable.

Altogether, there were 7,302 finishers who met the new qualifying times (based on their age at Chicago). If I applied the old qualifying times instead, the number would have been 9,371. Last year, the actual number of qualifiers out of Chicago was 9,379.

So the new qualifying times did reduce the number of qualifiers – but perhaps not by quite as much as you’d expect.

This visual breaks those numbers down by age and gender.

There were more men qualifying in most age groups than women. In part, this is a reflection of the imbalance in the number of finishers. But beneath the surface, it does appear that men qualified at a higher rate than women.

There’s also an interesting dynamic among older runners. The number of men 55-59 qualifying is almost equal to the number of men 60-64 – despite the younger age group being much larger. This is almost definitely a result of the qualifying times changing for runners under 60 and staying the same for runners 60+.

Exactly how much impact these qualifying times will have on different age groups is a topic for a much larger analysis. And I’ll get to that in the next couple of weeks.

Check out the full analysis on Medium for some more detail – including the distribution of qualifying times by how large their BQ buffers are.

What Did Think About the 2024 Chicago Marathon?

Did you run the Chicago Marathon this year? What did you think?

I was one of the 52,000 finishers at the race, and you can read my race report here. I had an amazing experience, and I thought it was a great race – despite being very crowded.

I’ve also created an interactive dashboard to help explore the results of the race. Check it out and let me know what you think.

And if you had any other questions about the data, feel free to drop a comment below.