Concerns cloud glee over strong gains on Wall St

New York

US stock investors head into the Thanksgiving holiday thankful for the market's recent strength, which puts major indices on track for another year of double-digit gains, though the swiftness of the advance has raised eyebrows.

The S&P 500 is up 13.7 per cent from an intraday low hit on Oct 15, and the gains since then have been broad. Since that bottom, all but 21 S&P 500 components are higher.