Probably the GMU you're picking.
I've never failed to draw 1st round or secondary as appropriate in 10+ years of going.
This year might be a skip year as I've a low chance of drawing for Muzzle in the GMU I applied, and the 3rd rifle guys are taking the year off for various reasons.
Sometimes it's as much about knowing how to work the draw choices and the GMU's you choose as it is tags issued.
If you get skunked on everything else, you can almost always get an OTC bull tag.