Earlier quoted context omitted.
Echoing recent discussions on HN, from wikipedia: "An article published in The New York Times in 2015 said that Simons was involved in one of the biggest tax battles of the year, with Renaissance Technologies being "under review by the I.R.S. over a loophole that saved their fund an estimated $6.8 billion in taxes over roughly a decade."[46] In September 2021, it was announced that Simons and his colleagues would pay…
Even with accounting for that change RenTec’s returns don’t change all too much.
RenTec's secret sauce has always been their tax attorneys, not their quants. Prior to this "retirement fund" issue, RenTec was notorious for tax avoidance schemes like claiming LT capital gains on basket options.