In this video from Friday's Market Checkup, Motley Fool health-care analyst David Williamson tells investors in the health-care sector why he has his eye on the Obamacare enrollment numbers at the moment.

So far, 800,000 people have signed up for private health plans through Obamacare in January, which boosts the total enrollment to 3 million with a week to go in the month. This shows that despite not reaching the Centers for Medicare and Medicaid Services' original enrollment expectations for January because of healthcare.gov's rocky rollout, there is no lull in enrollment momentum, as the pace continues to remain strong in 2014.

David looks in this segment at why managed-care insurers such as WellPoint (NYSE:ANTM), which have a large exchange footprint, should benefit as enrollment continues upward.