Strong first half by stocks usually bodes well for the rest of the year, history shows

• When the S&P 500's first-half gain was between 7 and 12 percent, the benchmark averaged a 5.1 percent during the second half, according to CFRA Research.
• If the benchmark follows the historical trend, that would put it at 2,565 to end the year.
• Strategist Sam Stovall notes the market could still be volatile, especially in the third quarter.

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The strong 8.9 percent rise since January bodes well for the second half of the year, if history is any guide. The nearly 9 percent boost represents more than twice the average increase during the first six months of all years since 1946 and more gains typically follow such a strong start to a year, according to a report from CFRA Research's Sam Stovall.

"When the 500's first-half price gain was between 7% and 12%, or the second-highest quintile of H1 returns, the market went on to record an average price rise of 5.1% during the second half," wrote the CFRA chief strategist in the Monday note. After such gains, the market "posted a positive H2 performance an above-average 87% of the time."

Source: CFRA

If the benchmark follows the historical trend, that would put it at 2,565 to end the year, about equal to Stovall's fundamental year-end target based on his estimates for earnings and economic performance. The S&P 500 closed Friday at 2,438.30.

To be sure, the strategist cautions it may not be as smooth a ride for investors as the first half. The S&P 500 averaged a 0.6 percent decline during the third quarter since 1990, Stovall notes.

There was no sign of volatility in the market Monday, however, as the CBOE Market Volatility Index (VIX) fell below 10.