If you thought the momentum sell-off was over, you were wrong. Stocks tumbled again today led by volatile, momentum names in industries like tech and biotech. By the end of the session, the Dow Jones Industrial Average (DJINDICES:^DJI) had shed 267 points, or 1.6%, while the S&P 500 was down 2.1%, and the Nasdaq plummeted 3.1%. It was the worst day for the tech-heavy Nasdaq since November 2011. Meanwhile, the Nasdaq Biotech Index lost a full 5.7%. There seems to be no better explanation for the recent selling than simple investor psychology. Investors may be beginning to believe that the market is overvalued after last year's run, or at least that the momentum names are overvalued. As the belief that a correction is imminent spreads, the selling only intensifies. Among the big names falling today were Facebook and Netflix, both losing more than 5%. Analysts also see just 1% earnings growth this season, which could be adding to the pessimism. 

Though investors were selling, the day's macroeconomic data was pointing in a different direction, as weekly initial jobless claims hit a seven-year low, falling from 332,000 a week ago to 300,000. That level was well below estimates of 325,000 -- a level that has not been seen since May 2007, before the recession began. Initial unemployment claims tend to be volatile, but the report bodes well for the labor market, and seems to indicate that the economy is improving along with the warmer weather. 

Among stocks bucking the downward trend today was Rite Aid (NYSE:RAD), which finished up 8.4% after reporting earnings this morning. The drugstore chain continued to show progress in its turnaround efforts, posting adjusted earnings per share of $0.10, well ahead of estimates at $0.04. Revenue, meanwhile, hit $6.6 billion on a same-store sales increase of 2.1%, beating estimates of $6.54 billion. CEO John Standley credited recent acquisitions of Health Dialog and RediClinic and the execution of key initiatives for the successful turnaround. Investors also liked Rite Aid's revenue guidance for the year, as the company sees sales of $26 billion-$26.5 billion on a same-store sales increase of 2.5%-4.5%. Analysts had expected revenue of $25.75 billion. Meanwhile, its EPS forecast of $0.31-$0.42 was in line with estimates of $0.35.

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Elsewhere, Family Dollar (UNKNOWN:FDO.DL) opened the day with a gain, but closed down 3.2% after its second-quarter report came out. The dollar-store chain said it would close hundreds of stores in a bid to reverse its current sales decline, as same-store sales fell 3.8%, and overall revenue fell 6.1%, to $2.72 billion, below estimates at $2.77 billion. Earnings per share of $0.80 missed the analysts' mark at $0.90. CEO Howard Levine said the results did not meet expectations, and said the company will reduce prices and costs, and close 370 underperforming stores in order to drive future profitability.