A Global Pace Paradox

When running data is more than it seems at first glance…

When we launched the Runkeeper Global 5k challenge in December, one of the things we were curious to find out was which country (on average) has the fastest runners. If you’ve read our blog post on the Global 5k results, you’ll already know that the answer is the Netherlands:

Overall pace from the Global 5k

1. Netherlands (5:53 per km/9:28 per mi)
2. Belgium (5:58 per km/9:36 per mi)
3. United Kingdom (6:00 per km/9:40 per mi)
4. France (6:02 per km/9:42 per mi)
5. Italy (6:08 per km/9:52 per mi)
6. Spain (6:08 per km/9:53 per mi)
7. Japan (6:08 per km/9:53 per mi)
8. Germany (6:10 per km/9:55 per mi)
9. Australia (6:10 per km/9:56 per mi)
10. Canada (6:12 per km/9:59 per mi)
11. Russia (6:14 per km/10:02 per mi)
12. Sweden (6:14 per km/10:08 per mi)
13. United States (6:19 per km/10:10 per mi)
14. Brazil (6:31 per km/10:30 per mi)
15. India (8:00 per km/12:53 per mi…must be all that traffic, yikes!)

Not so fast

This wasn’t actually the first answer we came up with. In our initial analysis, Italy (ranked #5 above) came in as the fastest, with a 9:25 min/mile median pace. The Netherlands was in second place, a fraction of a second slower. So: what changed?

The answer lies in something known as Simpson’s Paradox. In our first pass, we grouped all participants together. Not all runners are alike, though. Male participants in the Global 5k were generally a bit faster — the median pace for men was 9:12 min/mile and the median pace for women was 10:42 min/mile.

Italian runners were on average the fastest, true… but this was because the mix of runners in Italy was different than in most other countries. Most European countries skewed slightly male (55% — 60% male), but in Italy fully 75% of participants were male. The boost from all those fast-running men translated into an speedy overall pace for Italy!

Despite having the fastest overall median pace, Italy’s male runners ran at a median pace 16 seconds slower than men in the Netherlands, and its female runners ran 32 seconds slower than Dutch women. With Dutch men faster than Italian men and Dutch women faster than Italian women, it really wouldn’t be fair to say that Italy was the fastest country.

To solve this issue and create a final, “fair” pace for each country, we took a straight average of the male and female paces. Calculated this way, the pace in the Netherlands barely changes (since they were already 53% male / 47% female), but the pace for Italian runners slows down by 27 seconds to a 9:52 min/mile.

Italy and the Netherlands weren’t the only countries affected by this statistical quirk. The US and Brazil swapped places, since Brazil had 72% male runners while the US had just 47% male runners. Both countries still stayed near the bottom of the overall country rankings, though… better luck next time!