Investors’ cash positions dropped below a critical threshold in a monthly Bank of America Corp. survey, triggering a so-called sell signal for equities at a time of rising doubts around lofty technology valuations. The average cash held by global fund managers fell to 3.7%, something that has only occurred 20 times since 2002. Stocks declined and Treasuries outperformed in the following one-to-three months each time that happened, strategist Michael Hartnett wrote in a note. Most Read from Bloomberg Sto ...