pre_text: Income Tax Provision Reconciliation The difference between the income tax benefit (provision) and income taxes computed using the U.S. federal income tax rate was as follows for the years ended September 30, 2019, 2018, and 2017 (amounts shown in thousands):
table: 2019 2018 2017
table: Amount computed using statutory rate $841 $2,122 $(1,078)
table: Net change in valuation allowance for net deferred tax assets (459) (367) 10,058
table: AMT and other — (191) 20
table: Foreign rate differential 664 22 (169)
table: Non-deductible items (151) (276) (370)
table: State income tax (370) 50 (34)
table: Impact of tax reform on deferred taxes — (4,901) —
table: Research and development credits 1,694 475 2,494
table: Foreign income tax (494) — —
table: Stock compensation, net 1,539 — —
table: Income tax benefit (provision) $3,264 $(3,066) $10,921
question: Analyse this data from a financial earnings document. What is the sum of amount computed using statutory rate and foreign rate differential in 2018 as a percentage of 2019?