Our effective tax rate for the three and six months ended June 30, 2021 was 19.8 percent and 19.3 percent, respectively, compared to 19.8 percent and 13.0 percent, respectively, for the same period in 2020. Effective rates are dependent upon components of pretax earnings and the related tax effects. Pretax income, tax-favored adjustments and the effective rate was similar for the second quarters of 2021 and 2020. For the six-month period end June 30, the effective tax rate was higher for 2021 as lower pretax income was experienced in 2020, which increased the percentage impact of tax-favored adjustments.

Income tax expense attributable to income from operations for the three and six-month periods ended June 30, 2021 and 2020 differed from the amounts computed by applying the U.S. federal tax rate of 21 percent to pretax income by the items detailed in the below table. In interim periods, income taxes are adjusted to reflect the effective tax rate we anticipate for the year, with adjustments flowing through the other items, net line.

	For the Three Months Ended June 30,														For the Six Months Ended June 30,
	2021							2020							2021							2020
(in thousands)	Amount			%				Amount			%				Amount			%				Amount			%
Provision for income taxes at the statutory rate of 21%	$	21,424			21.0		%	$	24,124			21.0		%	$	40,290			21.0		%	$	7,458			21.0		%
Increase (reduction) in taxes resulting from:
Excess tax benefit on share-based compensation		(270	)		(0.3	)	%		(265	)		(0.2	)	%		(2,194	)		(1.1	)	%		(1,293	)		(3.6	)	%
Tax exempt interest income		(310	)		(0.3	)	%		(323	)		(0.3	)	%		(629	)		(0.3	)	%		(636	)		(1.8	)	%
Dividends received deduction		(248	)		(0.2	)	%		(212	)		(0.2	)	%		(484	)		(0.3	)	%		(484	)		(1.4	)	%
Investment tax credit		(801	)		(0.8	)	%		(129	)		(0.1	)	%		(1,603	)		(0.8	)	%		(1,449	)		(4.0	)	%
ESOP dividends paid deduction		(137	)		(0.1	)	%		(137	)		(0.1	)	%		(267	)		(0.1	)	%		(269	)		(0.8	)	%
Nondeductible expenses		826			0.8		%		161			0.1		%		1,237			0.6		%		364			1.0		%
Other items, net		(278	)		(0.3	)	%		(506	)		(0.4	)	%		678			0.3		%		925			2.6		%
Total tax expense	$	20,206			19.8		%	$	22,713			19.8		%	$	37,028			19.3		%	$	4,616			13.0		%