S&P 500 Movers: UA, MRK (1/16, 10:19 AM ET) -- In early trading on Tuesday, shares of Merck (MRK) topped the list of the day's best performing components of the S&P 500 index, trading up 6.1%. Year to date, Merck registers a 10.6% gain.

And the worst performing S&P 500 component thus far on the day is Under Armour (UA), trading down 5.8%. Under Armour is roughly unchanged. looking at the year to date performance.

Another component making moves today is Wynn Resorts (WYNN), trading up 3.8% on the day.

For MarketNewsVideo.com, I'm Sayoko Murase.