The effective tax rates for the three months ended March 30, 2019 and March 31, 2018 were 21.1% and (47.7%), respectively. For the three months ended March 30, 2019, the primary difference between the U.S. federal statutory tax rate and the Company’s consolidated effective tax rate was due to $1,462 of higher state income tax expenses versus the prior year period and a $856 tax expense related to global intangible low-taxed income (“GILTI”). The effective tax rate was partially offset by a $648 tax benefit related to foreign-derived intangible income (“FDII”). For the three months ended March 31, 2018, the primary difference between the U.S. federal statutory tax rate and the Company’s consolidated effective tax rate was due to the $18,105 tax benefit related to tax windfalls from stock compensation and a $1,859 tax benefit related to the cessation of operations of the Company’s Mexican subsidiary.

The differences between the U.S. federal statutory tax rate and the Company’s consolidated effective tax rate were as follows:

	Three Months Ended
	March 30,			March 31,
	2019			2018
U.S. federal statutory tax rate		21.0	%		21.0	%
State income taxes (net of federal benefit)		(10.8	%)		2.9	%
Cessation of operations		0.0	%		(7.0	%)
Research and development credit		2.3	%		(1.6	%)
Tax windfall on share-based awards		0.0	%		(68.5	%)
GILTI		(6.3	%)		0.0	%
FDII		4.8	%		0.0	%
Section 162(m) limitation		(1.4	%)		1.0	%
Increase in valuation allowance due to net operating loss		(2.2	%)		1.6	%
Impact of foreign operations		3.9	%		1.0	%
Other		9.8	%		1.9	%
Total effective tax rate		21.1	%		(47.7	%)