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. The estimated effective income tax rate was 34.66% and 34.63% for the three and six months ended June 30, 2016, respectively. The estimated effective income tax rate was 43.02% and 42.24% for the three and six months ended June 30, 2015, respectively. The lower effective income tax rate for the three and six months ended June 30, 2016 is primarily a result of the Section 199 qualified production activities deduction and the research and development tax credit.