The top aftermarket NYSE losers Monday were: Radioshack Corp, Ormat Technologies, Valeant Pharmaceuticals International, Plum Creek Timber Co, Senior Housing Properties Trust, Radian Group, InvenSense, National Bank of Greece SA, Best Buy Co and Demand Media Inc.

Radioshack Corp. (NYSE:RSH) shares slumped 19.75 percent to $8.21 in post market trading session after announcing unaudited results for the fourth quarter. The company expects diluted earnings to be in a range of $0.11 to $0.13 per share compared to $0.51 per share in the same quarter a year-earlier and against analysts' estimation of $0.37 for the fourth quarter.

Ormat Technologies, Inc. (NYSE:ORA) shares plunged 3.77 percent to $16.86 in post market trading session after announcing that revenue in 2012 will fall by an estimated $24.8 million.

Valeant Pharmaceuticals International, Inc. (NYSE:VRX) shares declined 3.14 percent to $47.21 in aftermarket trading session. The stock has a 52-week low of $32.05, a 52-week high of $57.24 and $15.01 billion in market capitalization.

Plum Creek Timber Co, Inc. (NYSE:PCL) shares declined 2.94 percent to $38.90 in post market trading session. The company announced fourth quarter net income of $61 million or $0.38 per share compared to $59 million or $0.37 per share in the same period a year-ago, while analysts' expected the company to report fourth quarter net profit of $0.39 per share.

Senior Housing Properties Trust (NYSE:SNH) shares declined 2.89 percent to $21.88 in post market trading session.

Radian Group Inc. (NYSE:RDN) shares declined 2.55 percent to $2.68 in aftermarket trading session.

InvenSense, Inc. (NYSE:INVN) shares declined 2.53 percent to $15.88 in aftermarket trading session. The stock has a 52-week low of $8.25, a 52-week high of $16.74 and $1.29 billion in market capitalization.

National Bank of Greece SA (NYSE:NBG) shares fell 2.48 percent to $3.15 in post market trading session.

Best Buy Co., Inc. (NYSE:BBY) shares declined 2.17 percent to $24.83 in post market trading session. The stock has a 52-week low of $21.79, a 52-week high of $35.45 and $8.89 billion in market capitalization.

Demand Media Inc. (NYSE:DMD) shares declined 1.93 percent to $6.60 in post market trading session.

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