A bear market may be underway, warns Nobel-winning economist Robert Shiller, so long as investor fears over an overvalued stock market stay at what is their highest level since the dot-com bubble in 2000. Shiller blames the tripling of stock prices over the past six years and the loss of people's confidence to have been driving this metric up in his indexes.

With recent increases in the CBOE Volatility Index as well as overall market volatility, people are "re-evaluating their exposure to the stock market," Shiller told the Financial Times. "And we could see aftershocks of the correction."

But what about that possible Fed hike? Not a "big deal," Shiller says, downplaying a market fallout. Similarly, the much-debated cyclically adjusted price-to-earnings ratio, or CAPE, has been showing stocks to have been overvalued over the past decade. "If I average over 10 years I don't see that as a problem," Shiller says. [CNBC]