(Bloomberg) -- At this point, most investors probably just want the year to be over to book their gains -- especially now that the Cboe Volatility Index is behaving in a way that’s preceded stock losses in the past.

The VIX, also known as Wall Street’s “fear gauge,” jumped 16% on Monday to 15.86, while the S&P 500 Index retreated just 0.3% and is still less than a percent away from its record high.

Citigroup Global Markets Inc. strategists William O’Donnell and Edward Acton saw the action as “very interesting,” noting that the VIX experienced a “bullish hammer reversal pattern against major horizontal support.” In other words, a technical indicator shows the gauge is likely to keep rising.

That happened just after the S&P 500 and VIX, which move in opposite directions about 80% of the time, rose in tandem for two straight weeks for the first time since early May. Back then, an almost 7% slump in the S&P 500 followed in the next month.

There are several events this week that may be spurring investors to hedge: rate decisions by the Federal Reserve and European Central Bank, and the Dec. 15 date the Trump Administration is set to impose tariffs on another $160 billion of imports from China.

Investors looking for levels on the VIX might want to focus on the 18 area, which represents half of the closing high from last December and is about 50% above this year’s low, according to strategist Todd Salamone of Schaeffer’s Investment Research. The 20 strike is another one to watch as that’s where heavy call-option open interest begins for the Dec. 18 expiration, he said in a note Monday.

Salamone highlighted one more key level -- the 24-25 zone, which would be a test of the year-over-year breakeven, as the VIX ended 2018 at 25.42.

To contact the reporter on this story: Joanna Ossinger in Singapore at jossinger@bloomberg.net

To contact the editors responsible for this story: Christopher Anstey at canstey@bloomberg.net, Cecile Vannucci, Lianting Tu

©2019 Bloomberg L.P.