13.	INCOME TAXES

The provision for income taxes is based on a current estimate of the annual effective income tax rate adjusted to reflect the impact of discrete items. Significant management judgment is required in estimating operating income in order to determine our effective income tax rate. Our effective income tax rate was 20.92% and 33.48% for the three months ended March 31, 2018 and 2017, respectively. The lower effective tax rate for the three months ended March 31, 2018 is primarily a result of the decrease in the federal corporate tax rate that went into effect in December 2017 with the enactment of the Tax Cuts and Jobs Act of 2017.