Quarterly report pursuant to Section 13 or 15(d)

Income Taxes

Income Taxes
9 Months Ended
Sep. 30, 2012
Income Taxes [Abstract]  
Income Taxes
10. Income Taxes

We make estimates and judgments in determining income tax expense for financial statement purposes. These estimates and judgments occur in the calculation of certain tax assets and liabilities, which arise from differences in the timing of recognition of revenue and expense for tax and financial statement purposes.

Our provision for income taxes in interim periods is based on our estimated annual effective tax rate. We record cumulative adjustments in the quarter in which a change in the estimated annual effective rate is determined. The estimated annual effective tax rate calculation does not include the effect of discrete events that may occur during the year. The effect of these events, if any, is recorded in the quarter in which the event occurs.

Our effective income tax rate was 36.4% and 19.4% for the three months ended September 30, 2012 and 2011, respectively, and 32.5% and 29.5% for the nine months ended September 30, 2012 and 2011. Our effective tax rate fluctuated from the prior period predominantly due to the impact of permanent differences, including stock compensation and the non-deductibility of contingent consideration, in relation to our results of operations before income taxes.