What does "lagged' of "the communications and tech sectors lagged" mean?


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The Dow dropped 350 points after falling more than 450 points, led by declines in Caterpillar and Apple. The S&P 500 fell 1.5 percent as the communications and tech sectors lagged. The Nasdaq pulled back 2 percent. Overseas, China's Shanghai Composite dropped fell sharply.

Thursday's decline added to the market's steep losses for this month. The Dow and S&P 500 have fallen more than 3 percent each, while the Nasdaq is down more than 6.5 percent.

Among the reasons for selling Thursday, according to investors, were the falling Chinese stock market, worries about a slowing global economy and a jump in Italian bond yields.