Such a precipitous increase in the value of U.S. equities has stirred up the usual cacophony of equity-bears screaming “bubble!” “Bubble” is a popular term, but, as it turns out, is rather ill-defined and fuzzy.

One thing for certain is that financial markets face more uncertainty than usual right now. So it’s tougher to forecast economic and political trends, and to model investment and business risk based on those expectations, at a time that seems more of a major upheaval than a momentary shift.

Warren Buffett is responsible for putting up tremendous returns as CEO of Berkshire Hathaway. In the first quarter of 2016, Berkshire bought shares in Apple (NASDAQ: AAPL). While Buffett typically shied away from making investments within the tech sector,