Stocks ended a wobbly week broadly lower, with much of Friday's loss attributable to weakness in big technology companies like Apple and Amazon.

The S&P 500 index fell 0.8% and marked its first weekly loss after three weeks of gains.

Small-company stocks continued to badly lag the rest of the market, a signal that investors could be becoming more concerned about how strongly the economy will keep growing in coming months.

Treasury yields remained relatively low, another sign of caution among investors.

The yield on the 10-year Treasury note held steady at 1.29%, well below the 1.75% it fetched in late March.