Fiscal Years
2019
2018
2017
Federal statutory rate
21.0%
24.5%
35.0%
Foreign rate differential
1.6
5.1
31.9
State taxes net of federal benefit
0.9
0.8
0.2
Warrant liabilities
—
4.4
(1.8)
Change in valuation allowance
(2.4)
34.0
(270.0)
Research and development credits
1.4
9.0
12.8
Provision to return adjustments
0.3
8.3
(4.0)
Section 382 adjustment
(19.3)
—
—
Nondeductible compensation expense
(0.6)
1.4
(4.1)
Global Intangible Low Taxed Income
(2.9)
—
—
Nondeductible legal fees
—
0.9
(3.9)
2017 tax reform
—
(73.7)
—
Intra-entity license transfer
9.4
—
—
Other permanent differences
(0.1)
(0.9)
0.1
Effective income tax rate
9.3%
13.8%
(203.8)%

text: The $252.5 million of valuation allowance as of September 27, 2019 relates primarily to federal and state NOLs, tax credit carryforwards and a partial valuation allowance on tax credits in Canada of $19.0 million whose recovery is not considered more likely than not. The$243.1 million of valuation allowance as of September 28, 2018 related primarily to federal and state NOLs, tax credit carryforwards and a partial valuation allowance on tax credits in Canada of$13.6 million whose recovery is not considered more likely than not. The change during the fiscal year endedSeptember 27, 2019 of $9.4 million primarily relates to the reduction of our NOLs due to section 382 limitations, the changes in our temporary differences, and the lower U.S federal tax rate.
text: Our effective tax rates differ from the federal and statutory rate as follows:
text: For fiscal years 2019, 2018 and 2017, the effective tax rates on $423.2 million, $155.2 million and $49.5 million, respectively, of pre-tax loss from continuing operations were 9.3%, 13.8% and (203.8)%, respectively.
text: For fiscal year 2019, the effective tax rate was primarily impacted by a change in our NOL carryforward due to an adjustment in our Section 382 limitation from a prior period acquisition and the immediate recognition of the current and deferred income tax effects totaling $39.8 million from an intra-entity transfer of a license for intellectual property to a higher taxed jurisdiction that received a tax basis step-up.
text: For fiscal year 2018, the effective tax rate was primarily impacted by the Tax Cuts and Jobs Act (the "Tax Act"). The effective income tax rates for fiscal years 2019, 2018 and 2017 were also impacted by a lower income tax rate in many foreign jurisdictions in which our foreign subsidiaries operate, changes in valuation allowance, research and development tax credits, and a fair market value adjustment of warrant liabilities.
text: All earnings of foreign subsidiaries, other than our M/A-COM Technology Solutions International Limited Cayman Islands subsidiary ("Cayman Islands subsidiary"), are considered indefinitely reinvested for the periods presented. During fiscal year 2019 we changed our position for our Cayman Islands subsidiary to no longer have its earnings permanently reinvested.
text: Although a foreign subsidiary would typically have to accrue for foreign withholding tax liabilities associated with undistributed earnings, Cayman Islands has no withholding tax under domestic law, therefore, we did not accrue for foreign withholding tax.
text: During fiscal year 2019 we finalized our calculation of the one-time deemed repatriation of gross foreign earnings and profits, totaling $156.8 million, which resulted in approximately $86.7 million in U.S. taxable income for the year ended September 28, 2018 with Grand Cayman and Ireland accounting for$ 59.7 million and $25.6 million, respectively. Due to the fact that we are in a full U.S. valuation allowance, this one-time deemed repatriation had no impact on our tax expense for fiscal year 2018.
text: Our fiscal year 2019 tax provision incorporated changes required by the Tax Act. Some of these changes include a new limitation on the deductible interest expense, inclusion of Global Intangible Low Taxed Income earned by controlled foreign corporations, computation of the new base erosion anti-abuse minimum tax, repealing the performance-based compensation exception to section 162(m) and revising the definition of a covered employee.

Questions:
question: What was the respective effective income tax rate in 2019, 2018 and 2017?
answer: 9.3%
13.8%
(203.8)%
question: What was the respective foreign rate differential in 2019, 2018 and 2017?
answer: 1.6
5.1
31.9
scale: percent
question: What was the Federal statutory rate in 2019?
answer: 21.0
scale: percent
question: In which year was Foreign rate differential greater than 10.0?
answer: 2017
derivation: locate and analyze Foreign rate differential in row 4
question: What was the average State taxes net of federal benefit for 2017-2019?
answer: 0.63
derivation: (0.9 + 0.8 + 0.2) / 3
scale: percent
question: What is the change in the Research and development credits from 2018 to 2019?
answer: -7.6
derivation: 1.4 - 9.0
scale: percent