Since last Friday, shares of the digital audio company Sirius XM Holdings ( SIRI -3.06%) are now trading 13.5% lower as of 1:52 p.m. ET Thursday. Sirius, a stock Warren Buffett's Berkshire Hathaway has been piling into, fell after the company's chief financial officer (CFO) spoke about concerns for the sector.

Warren Buffett is rightly called the greatest living investor. Since becoming CEO of Berkshire Hathaway (NYSE:BRK-A)(NYSE:BRK-B) in 1965, Buffett has generated cumulative returns 5,502,284%, a nearly 20% annual return,

Over the last five years, Americans have watched equity markets soar. Just last month, the S&P 500 reached an all-time high of 6,144, up over 89% from January 2020. Such a precipitous increase in the value of U.S. equities has stirred up the usual cacophony of equity-bears screaming “bubble!”