NEW YORK ( TheStreet) -- Despite the Federal Reserve's move toward maximum accommodation and a quarter from Apple ( AAPL) that sent Wall Street straining for superlatives, the S&P 500 tallied a gain of less than a point last week. The Dow Jones Industrial Average dipped 0.5%, logging its first down week of the year, raising the question of whether the rally is getting a little long in the tooth just as January winds down. Are the bulls losing some steam or just catching their breath? Year to date, the major U.S. equity indices are still in great shape. The Dow has tacked on 3.6%, the S&P 500 is up 4.7%, and the Nasdaq Composite has ridden fairly strong results from the tech sector to an 8.1% advance. Apple's 6%-plus gain last week (allowing it to snatch the title of world's largest company by market cap from Exxon Mobil ( XOM), $417 billion vs. $411 billion) was a big contributor to the Nasdaq's outsized surge. After a mostly flat year in 2011, when appreciation was generally limited to the large caps and dividend payers, this rally has been greeted with tentative optimism. Yes, the move has come on low volumes amid middling earnings growth. But the economic data have been getting incrementally better, and the European Central Bank's long-term refinancing operation has brought some stabilization to the situation there, even though much work remains to be done. Throw in festering hopes that Fed Chairman Ben Bernanke has another dose of quantitative easing up his sleeve sooner rather than later, and there's your bounce. TrimTabs doesn't like what it sees and is getting cautiously bearish, or 50% short, on U.S. stocks. Its main motivation is a drop in its proprietary demand index, which "uses 21 flow and sentiment regressions," such as fund flow data, to time the U.S. stock market. The firm said Sunday the index closed at 27.0 on Jan. 26, its lowest reading since September 2009 and down 59.7 points from an interim peak at 86.7 on Dec. 30. Readings of more than 50 are considered bullish. "The bullish camp has become crowded following the low-volume melt-up of the past month, but few of our key indicators suggest the rally will continue," TrimTabs said. "The most dramatic change recently has come on the demand side ... The only factors providing significant positive support to the TTDI are low levels of cash at equity mutual funds and low levels of assets at retail money market funds." For its part, Birinyi Associates says the 20%-plus run-up in the S&P 500 off the October lows is actually a positive sign in and of itself. The research firm notes the index has gained 20.63% since Oct. 3, a stretch of 78 trading days. This has happened 15 other times since 1945, Birinyi, says, about once every four years. The index's track record in the wake of such a move is pretty darn good. The average performance over the next six months is a gain of 6.96%, and the S&P 500 has declined in only two of the previous 15 instances. Meanwhile, Capital Economics thinks QE3 is still on the menu for the first half of the year, which should only embolden the bulls.