Yes. It’s basketball in the NCAA tournament specifically.

It’s easy when you see it but it sounds complicated to explain.

The tournament has 64 teams split into 4 regions. In each region, every team has a ranking between 1 and 16 and the teams play each other. A winning team advances to the next round and the losing team is eliminated.

This chart is examining the sum of the seed numbers of the teams that make it to the third round (called the sweet 16) each year in the tournament.

If better (lower) ranked teams beat the higher ranked teams, the sum of the seeds will be lower. This implies that there are fewer upsets.

Statistically, lower seeds are less likely to advance to the final stages. Still, in some years, higher seeds make it to the sweet sixteen and beyond. In such cases, the sum will be much higher and implies there were more upsets in the tournament that year.