rosh hashanah apples and honeySell Rosh Hashana and buy Yom Kippur, the old Wall Street adage has it. A new study by researchers at a Florida university validates the Stock Trader’s Almanac trick enshrined on page 88 of the classic compendium of historical market data.

Researchers at Nova Southeastern University in a just released study say the strategy does indeed boost stock market returns. Pan Yatrakis, who co-authored the study with Albert Williams, said in a news release last week:

“Observant Jewish traders represent a small proportion of all market participants but, at the margin, their withdrawal during the High Holy Days thins out the market, increases volatility and risk, and may discourage others from trading as well, thus creating a snowball effect.”

The South Florida Business Journal reports that the study looked at closing values of the Dow Jones Industrial Average from 1907 to 2008 and found that selling stocks before Rosh Hashana and buying after Yom Kippur netted a 1% average return.

The study adds to findings by other scholars confirming that trading volume declines significantly on both Rosh Hashana and Yom Kippur, associating the former with positive returns and the latter with sharp sell-offs.

But what’s known as the “Jewish Holiday effect” is chump change compared to the real import of the holidays, a 10-day period known as the Days of Awe when Jewish tradition holds that God decrees the fate of all mankind for the year ahead.

On Rosh Hashana Jews believe that God decrees everything from who will live and who will die to how a person will earn his livelihood down to the last red cent (or shekel, as the case may be). The interim 10 days give Jews a chance to improve the decree through sincere efforts to repair their relationship with the Almighty through prayer and charity.

Despite the gravity of the occasion, Jews approach the period with a strong sense of optimism, celebrating Rosh Hashana with a festive meal, dipping apples in honey to symbolize their expectation of a good and sweet new year. Perhaps the best known feature of the holiday is the sounding of the shofar, a curved ram’s horn whose stirring sounds evoke both weeping and laughter and is meant to awaken Jews from their spiritual slumber and hasten their recommitment to their mission in life.

Rosh Hashana begins at nightfall Wednesday and ends at nightfall on Friday.