Amerigroup Shares Plunged: What You Need to Know

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: Shares of Medicaid coverage provider Amerigroup (NYSE: AGP  ) sank as low as 25% on Friday after its quarterly results disappointed Wall Street. 

So what: Hurt by a one-time charge associated with a premium adjustment in Georgia, Amerigroup posted a second-quarter profit of $0.83 per share, down from $1.31 per share in the year-ago period. The shares have been on a tear in recent months, up 50% in 2011 alone, so it's no surprise that the earnings drop is triggering Amerigroup's biggest share price sell-off in years.

Now what: I wouldn't be so quick to pounce on this sell-off. The Georgia issue has raised a cloud of uncertainty over the space, with Medicaid-dependent insurers WellCare (NYSE: WCG  ) and Centene (NYSE: CNC  ) also experiencing big losses today. Add the fact that higher-than-expected operating costs and a health-benefits ratio also led Amerigroup to miss estimates on an adjusted basis, and it's an easy decision to stay away.

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