The Nasdaq Composite, the US market index most closely associated with technology stocks, closed at an all-time high on Thursday, surpassing a 2000 record set just before the dotcom crash. Its record close of 5,056.06 capped a slow, unsteady climb from a 2002 low of 1,114.11 that spanned a recession, the rise of biotech and social media, and the explosive growth of mobile phones that has helped make Apple the most valuable company in the United States.