What is the change in total income tax expense between 2019 and 2018?
{"Current income tax expense: -- Federal ": {"December 27, 2019 ": 4003, "December 28, 2018 ": 2945, "December 29, 2017": 3342}, "Current income tax expense: -- State ": {"December 27, 2019 ": 2144, "December 28, 2018 ": 1943, "December 29, 2017": 1403}, "Current income tax expense: -- Total current income tax expense ": {"December 27, 2019 ": 6147, "December 28, 2018 ": 4888, "December 29, 2017": 4745}, "Deferred income tax expense (benefit): -- Federal ": {"December 27, 2019 ": 1617, "December 28, 2018 ": 2363, "December 29, 2017": -1059}, "Deferred income tax expense (benefit): -- Foreign ": {"December 27, 2019 ": 17, "December 28, 2018 ": -472, "December 29, 2017": 215}, "Deferred income tax expense (benefit): -- State ": {"December 27, 2019 ": 429, "December 28, 2018 ": 663, "December 29, 2017": 141}, "Deferred income tax expense (benefit): -- Total deferred income tax expense (benefit)": {"December 27, 2019 ": 2063, "December 28, 2018 ": 2554, "December 29, 2017": -703}, "Deferred income tax expense (benefit): -- Total income tax expense": {"December 27, 2019 ": 8210, "December 28, 2018 ": 7442, "December 29, 2017": 4042}}
total_income_tax_expense_2019 = df["Deferred income tax expense (benefit): -- Total income tax expense"]["December 27, 2019 "]
total_income_tax_expense_2018 = df["Deferred income tax expense (benefit): -- Total income tax expense"]["December 28, 2018 "]
answer = total_income_tax_expense_2019 - total_income_tax_expense_2018