What was the percentage change in Notional U.S. federal income tax expense at the statutory rate in 2019 from 2018?
{"Notional U.S. federal income tax expense at the statutory rate (1)": {"2019": 406, "2018": 551, "2017": 602}, "Adjustments to reconcile to the income tax expense (benefit): -- U.S. state income tax benefit, net": {"2019": -5, "2018": -7, "2017": -4}, "Adjustments to reconcile to the income tax expense (benefit): -- Tax law changes": {"2019": 15, "2018": 638, "2017": 7}, "Adjustments to reconcile to the income tax expense (benefit): -- Tax credits": {"2019": -22, "2018": -8, "2017": -8}, "Adjustments to reconcile to the income tax expense (benefit): -- Non-U.S. net earnings(2)": {"2019": -166, "2018": -213, "2017": -355}, "Adjustments to reconcile to the income tax expense (benefit): -- Change in accrued income tax liabilities": {"2019": -61, "2018": 13, "2017": 24}, "Adjustments to reconcile to the income tax expense (benefit): -- Valuation allowance": {"2019": -163, "2018": 33, "2017": -1}, "Adjustments to reconcile to the income tax expense (benefit): -- Legal entity restructuring and intercompany transactions": {"2019": 3, "2018": -1329, "2017": -40}, "Adjustments to reconcile to the income tax expense (benefit): -- Excess tax benefits from share-based payments": {"2019": -8, "2018": -24, "2017": -40}, "Adjustments to reconcile to the income tax expense (benefit): -- Other": {"2019": -14, "2018": 2, "2017": -5}, "Adjustments to reconcile to the income tax expense (benefit): -- Income tax expense (benefit)": {"2019": -15, "2018": -344, "2017": 180}}
notional_us_federal_income_tax_expense_at_the_statutory_rate_1_2019 = df["Notional U.S. federal income tax expense at the statutory rate (1)"]["2019"]
notional_us_federal_income_tax_expense_at_the_statutory_rate_1_2018 = df["Notional U.S. federal income tax expense at the statutory rate (1)"]["2018"]
answer = ( notional_us_federal_income_tax_expense_at_the_statutory_rate_1_2019 - notional_us_federal_income_tax_expense_at_the_statutory_rate_1_2018 ) / notional_us_federal_income_tax_expense_at_the_statutory_rate_1_2018 * 100.0