Income Tax Provision

3 Months Ended

Mar. 31, 2019

Income Tax Disclosure [Abstract]

Income Tax Provision

Income Tax Provision

We had an effective income tax rate of 22.0% for the three months ended March 31, 2019, compared to 4.1% for the three months ended March 31, 2018. The effective income tax rates for the periods presented were different from the statutory United States federal income tax rate of 21% due to excess tax benefits related to stock option exercises, state income taxes, non-deductible business expenses, and the tax benefit of research tax credits. The excess tax benefit related to stock option exercises realized was $1.7 million for the three months ended March 31, 2019, compared to $9.1 million for the three months ended March 31, 2018. Excluding the excess tax benefits, the effective rate was 26.8% for the three months ended March 31, 2019, compared to 27.2% for the three months ended March 31, 2018.

The increase in the effective tax rate for the three months ended March 31, 2019, as compared to the same period in 2018 was principally due to the decrease in excess tax benefit related to stock option exercises.

We made tax payments of $88,000 and $218,000 in the three months ended March 31, 2019, and 2018, respectively.