5.	Income Taxes

The Corporation’s effective income tax rates for the six months ended June 30, 2016 and 2015 were 30.4% and 30.2%, respectively. The estimated effective income tax rates reflect 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.

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