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13. Equity (Detail) - (Table 4) Summary of the Weighted-Average Grant Date Fair Value of Options Granted	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Expected dividend yield	0.00%	0.00%
Expected term (in years)	2.5 - 6.5	6.0 - 6.5
Expected volatility	70.00%	70.00%
Pre-vesting forfeiture rate	2.00%	2.00%

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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