By Alexis Xydias Nov. 16 (Bloomberg) -- Late-day sell-offs in the U.S. stock market this month may have been triggered by so-called quantitative funds dumping their holdings, according to analysts at Birinyi Associates Inc. The last 30 minutes of trading accounted for 80 percent of the losses in the Dow Jones Industrial Average between Nov. 7 and Nov. 15, data compiled by Birinyi show. When global equity markets tumbled in August, 65 percent of the declines were in the final half hour of trading, the research and money management firm said. ``We wonder if there are not again some quant funds experiencing deja vu,'' Jeffrey Rubin, director of research at Birinyi, said in an interview from Westport, Connecticut. ``There are some similarities now with the July-August period that I don't think should be ignored.'' Quantitative managers, who use mathematical strategies to make investments, were blamed by some investors for a sell-off that wiped out almost $400 billion in value from the Dow average from July 19 through Aug. 16. Funds were forced to sell because many owned the same holdings and ran similar computer models that were equally jarred by widening credit spreads and increasing stock-price volatility. Goldman Sachs Group Inc.'s Global Alpha hedge fund fell 22.5 percent in August on losses from stock and currency trades. New York-based Goldman, the world's largest securities firm, blamed the decline on too many quantitative funds making the same trades. Quantitative strategies may have a relatively bigger effect in the market at the end of the trading session because many computers are programmed to trade at that time and more stock is available to buy and sell as traders settle their transactions, Birinyi's Rubin said. Dow's Gyrations The Dow industrials yesterday erased their gain in the afternoon and touched their intraday low about 20 minutes before trading ended. The 30-stock gauge fell as much as 1.3 percent after earlier rising 0.2 percent. On Nov. 14, the benchmark gave up an advance in the last half hour. A rally by Palo Alto, California-based Hewlett-Packard Co. helped push the Dow average up 0.1 percent as of 2:05 p.m. today in New York. The measure earlier fell as much as 0.3 percent. For Manolis Liodakis, a quant strategist for New York-based Citigroup Inc., the late-day slumps by themselves aren't an indication that funds are selling holdings. `Correlation' The divergence in returns on various quantitative strategies monitored by the analyst offers no evidence the funds are being forced to sell, unlike in August when most models were performing in similar fashion. ``What I want to see before assessing whether this is quant selling is an increase in factor correlation,'' he said in London. ``Nothing of what I see now reminds me of what I saw in August.'' Khuram Chaudhry, European equity strategist for New York- based Merrill Lynch & Co., says that ``technical'' rather than ``fundamental'' funds may be the ones selling. Technical funds typically invest in stocks based on their correlations with other securities such as currencies and commodities, while fundamental funds tend to focus on share- price valuations or prospects for earnings growth. The yen's increase this month against the dollar and the jump in gold prices since August may have resulted in losses for some technical strategies, Chaudhry said. ``There is increased volatility in markets,'' the London- based strategist said. ``Those people who fail to understand the changes of the cycle are those most vulnerable, particularly the technical ones.''