Nassim Taleb.Mohd Zakir/Getty Images"The Black Swan" author Nassim Taleb says he's focused on hedging against a market collapse.He said the market is flashing parallels to prior crashes, noting that it is the most fragile in 20 years.He pointed to risks like high debt levels and "crazy" stock prices in an interview with Bloomberg.A top economist and risk expert says the US is in one of the most precarious investing environments in decades — and while some investors are cheering on the rally in stocks, he has his eye on a potential market collapse.Nassim Taleb, author of "The Black Swan," the famed treatise on the risks related to improbable events, aired concerns over the state of the market in a recent interview with Bloomberg.