Boston Scientific’s Worst Day in 25 Years Surprised Analysts

Few analysts foresaw the disappointing results and profit forecast that sent Boston Scientific Corp.’s shares plummeting nearly 20% this week. Even fewer have given up on their bullish calls since.

It’s a development that has surfaced time and again in the past year, and one that investors say throws into sharp relief a fundamental problem with equity research: how Wall Street’s almost unfailingly positive analysis often leaves investors blindsided when trouble hits.