national avg: 41% - so 5 fewer on the year. Small sample sizes cause big swings.
It's generally more complicated to get much out of it because teams are very judicious in when they take the risk - so they're probably going to go for it more when they're in 4th and short. Sample sizes are all over the place, much less consistent than third downs.
Push come to shove, 3/4th conversions are made on 1/2 down, here's 3rd down conversions in the cfp era by distance to gain.