The November U.S. stock-market rally has gotten a big boost from corporations buying back their shares, and computerized trend-following funds adding to their bullish bets, according to data from Bank of America and UBS Group.

According to the latest report on client fund flows from BofA, corporate buybacks last week were the second-highest recorded by the BofA team going back to 2010 as a percentage of the S&P 500’s total market capitalization. Last week also marked the second week in a row that the pace of corporations’...