Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Managed health care provider Amerigroup (NYSE: AGP) had an unhealthy day today, dropping 12% in intraday trading today after Medicare cuts were announced late Friday.

So what: Medicare announced an 11% reduction in rates for its skilled nursing facilities, effective next fiscal year. The Centers for Medicare & Medicaid Services also said there was an unexpected increase in nursing home payments this fiscal year.

Now what: A hoped-for 1.5% funding increase for skilled nursing facilities is now off the table. Stocks of Humana (NYSE: HUM), WellCare Health Plans (NYSE: WCG), UnitedHealth Group (NYSE: UNH), WellPoint (NYSE: WLP), Aetna (NYSE: AET), and Cigna (NYSE: CI) are also ailing today. The sell-off follows on the heels of another big plunge last Friday, after Amerigroup reported disappointing earnings.

Interested in more info on Amerigroup? Add it to your watchlist by clicking here.