Which sites appear most often in the Hot Network Questions list?

Is there any data about which Stack Exchange sites have their questions end up in the Hot Network Questions list the most? In particular:

1. What percentage of hot network questions comes from each site?
   1. What about all-time, this year, this month?
2. What percentage of questions from each site end up in the list? (It seems that a high percentage of all CodeGolf.SE questions end up here.)
3. Which site's questions stay on the list the longest?

And so on. Is there any data on these and similar questions?