These numbers are for OTs 2011 through 2020 (and some stray 2021 hires), for active or senior judges who have fed at least two clerks to the Supreme Court. If you're just interested in the totals, you can look at the last column. But I thought it was interesting to see the breakdowns by justice as well.

Garland remains the heaviest hitter, but also-rans Katzmann, Griffith, Tatel, and Wilkinson are posting nearly equivalent numbers. Remarkably, the top ten judges account for almost 40% of the clerks sent to the Court over the last ten years.
The top-line totals hide some of the feeding power of more recently appointed judges. So I've calculated per-term numbers below:

Katsas's numbers are astronomical. If he keeps up this pace, he'll rival Garland or Kavanaugh.
This tabulation also shows that five judges (Srinivasan, Pillard, Watford, Barron, and Friedland) have emerged as the Obama-era feeders. No other circuit-level Obama appointee has fed more than one clerk to the Court. (And no Trump appointee save Katsas.)
I also thought it would be interesting to see which judges fed to which half of the Court. For instance, despite Garland's current status as the most prominent feeder judge, he hasn't fed a clerk to Kavanaugh, Alito, Gorsuch, or Thomas (or Scalia) in the last ten years. The same is true for Katzmann.
Here are the per term numbers for judges feeding to the left of the Court (SS, RBG, EK, SB):

Notably, Griffith and Wilkinson fall out of the top five. Srinivasan, Fletcher, and Pillard begin to look like heavy hitters.
Here are the same numbers for the right (JGR, BMK, SA, NMG, and CT):

Katsas takes the top spot, by a comfortable margin. Garland, Katzmann, and Tatel disappear from the list.