T-Shirt sizes distribution for conference

With BarcampLjubljana just a week away, we’re also looking into providing T-Shirts for speakers (as an extra incentive to speak).

Since I’ve been at the number of events, I always wondered how organizers figure out how many different sizes to order and what would be optimal sizes distribution to keep most people happy. Since searching the Internet didn’t return much results I tried the crowd-sourcing route.

The most interesting results were from Event planning and Management group on LinkedIn with  exact size distribution by Andrea and anecdotal advice from Julius that “S” sizes are in highest demand. On top of that Valentin shared with me his exact size distribution. On top of that I’ve also found a Gay T-Shirt rights mail bulk order, that also gives some numbers.

To get better idea, I’ve plotted these numbers:

Surprisingly enough, even though anecdotal evidence (even in my experience), prefers smaller sizes the proposed numbers use prefer bigger sizes.

There is also another data that was kindly linked to me by John on Twitter. It’s a size distribution statistics of T-Shirts at Linux Symposium in years 1999 and 2008:

While we have just relative sizes, it does seem that there is trend towards bigger people. I can only hope that these size differences are here because different parts of the world treat “Large” size differently and not because we’re all getting collectively fatter.