6.	Income Taxes

The Company’s effective income tax rate for the nine-months ended September 30, 2017 was 26.2%. The effective income tax rate reflects the effect of federal and state income taxes and the impact of differences in book and tax accounting arising from the net permanent benefits associated with the statutory depletion deduction for mineral reserves and the domestic production deduction. For the nine-months ended September 30, 2017, as a result of the adoption of ASU 2016-09 (see Note 1), the effective income tax rate reflects the excess tax benefit related to the vesting and exercise of stock-based compensation awards, which are treated as discrete events, and had a favorable impact of 130 basis points on the tax rate. As previously stated in Note 1, this requirement of ASU 2016-09 is prospective and therefore, the prior-year effective income tax rate of 30.6% is not comparable.

The Company records interest accrued in relation to unrecognized tax benefits as income tax expense. Penalties, if incurred, are recorded as operating expenses in the consolidated statements of earnings and comprehensive earnings.