The S&P Global source data[1] has a list of the top 20 Q4 buyback totals, as well as their buyback numbers for selected historical periods. It would be interesting to see how much debt those companies took on during those periods. The top company over the past 5 years, Apple, has been notorious for sitting on a massive cash reserve.

[1] http://press.spglobal.com/2019-03-25-S-P-500-Q4-2018-Buyback...