After three years of non-stop gains in the U.S. stock market, investors are loading up on insurance at the first sign of trouble.

An index that tracks the cost of options used to hedge against a plunge in the Standard & Poor?s 500 Index has jumped to the highest level in almost 16 years, according to data compiled by Bloomberg. Stocks fell and volatility surged yesterday, sending the benchmark gauge for U.S. equities to its biggest loss in seven weeks, on concern over the outlook for Chinese stimulus and the health of the U.S. economy.

Speculative stocks have suffered bigger losses as investors sold their best performers and companies with the highest valuations. When the Russell 3000 Index (RAY) touched an intraday record at the end of last week, fewer than 55 percent of its components traded above their 200-day moving average, a combination that hasn?t happened since the peak of the dot-com bubble, according to MKM Partners LLC.

To read this article in its entirety click here.