Stocks may have nothing to fear but a lack of fear itself.
Over the past four sessions, the CBOE Volatility Index has fallen more than 13 percent, as the S&P 500 has climbed to record highs. In fact, on Monday, the VIX was trading just off the one-year lows it reached Friday.
What's interesting is that over the past 10 years, the S&P has performed rather poorly after the VIX has fallen 13 percent or more over four sessions. In the week that followed, the S&P 500 has experienced an average loss of 0.12 percent, versus an average gain of 0.24 percent, according to a study performed using analytics tool Kensho.
The VIX is computed from the prices of options on the S&P 500, and explicitly measures trader expectations of volatility over the next 30 days. But since index options are more frequently used to hedge against downside than to speculate on upside, the VIX tends to measure short-term investor nervousness — and is consequently referred to as the market's "fear gauge."
While the 0.36 percent performance differential may not sound huge, it could suggest that the market has a bit more to prove in the days after investors get more comfortable about owning stocks.
At the present time, "I think we are getting a bit too complacent," macro trader Boris Schlossberg of BK Asset Management said Friday on "Trading Nation." "I would actually want to be buying volatility before September, before October, on the assumption you're going to get some turbulence there."
Unsurprisingly, given the stat about S&P performance, the VIX has shown a tendency to bounce back; after falling 13 percent or more over four sessions, the VIX has risen an average of 2.5 percent, versus an average drop of 1.8 percent across all periods.
It is worth noting that investors cannot take long or short positions in the VIX outright, but they can bet on or against volatility by using futures or options.
Disclosure: CNBC parent NBCUniversal is a minority investor in Kensho.