Investors could see more volatility and lower returns from stocks next year—at least if history is any guide.

Market historian Sam Stovall, chief investment strategist at CFRA, notes the amount of new highs the S&P 500 hit in 2017, along with low volatility and wide dispersion between sectors, bodes ill for stocks.

Through Dec. 22, 2017, the S&P 500 set 62 new all-time highs versus an average of 29 in the years since WWII in which at least one new high was recorded, Stovall said in a year-end report. And the market hit these new highs while moving up or down by one percent or more on just eight days, versus an average of 50 such days per year since 1945.

Following years like 2017 marked by above-average new highs and below-average volatility, the S&P 500 gained an average of only 3.1 percent and rose in price only 55 percent of the time, versus an average annual advance of nearly 9 percent with a rise about 75 percent of the time, Stovall said. What’s more, volatility picked up in subsequent years to rival the normal average of 50 big-movement days, Stovall said.

Year-to-date through last Friday, the sector dispersion (the difference between the best- and worst-performing industry groups) was 43.9 percentage points, exceeding the average dispersion of 43.5 points since 1990.

Since 1945, the S&P 500 gained an average of only 1.9 percent and rose in price only 57 percent of the time in the year after an above-average dispersion, Stovall said.

Rather than assume the advance will continue as it has this year, “history advises that [investors] would be better off anticipating an increase in volatility, a reduction in new highs, as well as a below-average price gain for … the year ahead,” Stovall said.