12.	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 33.48% and 34.61% for the three months ended March 31, 2017 and 2016, respectively. The lower effective income tax rate for the three months ended March 31, 2017 is primarily a result of increases in the Section 199 qualified production activities deduction and the research and development tax credit.