The S&P 500 dropped 0.45%, to 1,562.17 points.
Humana shares closed higher by 8.6% at $75.02 before the Centers for Medicare & Medicaid Services announced that costs per person would be lower in 2014 than in 2013.
Following Thursday's record close, investors appeared to be looking for an excuse to take profits, and less-than-expected data on U.S. manufacturing provided the justification.The Institute for Supply Management said its manufacturing index for March was 51.3, trailing the 54.2 consensus expectation among economists surveyed by Thomson Reuters. A number higher than 50 suggests that the sector is growing whereas a number lower than the threshold reflects contraction. Last month's report showed a 1.1 point increase to 54.2. "Right now I think everyone is anticipating the spring slide, and so everyone is looking for some kind of data to indicate which way the teeter-totter is going to tip," said Frank Fantozzi, CEO of Planned Financial Services. U.S. Steel lost 4% to fall to its lowest in almost seven months as the company absorbed the effects of the latest manufacturing report. The Dow Jones Industrial Average was off 0.04%, at 14,572.85 on Monday. The Nasdaq dropped 0.87% to 3,239.17. Tesla Motors (TSLA - Get Report) was one of the top performers on the Nasdaq on Monday after the company announced that its electric sedan sales exceeded guidance and expected to show a profit in the first quarter. Shares jumped 16% to $43.93.