What was the change in the Total income tax expense between 2018 and 2019?
{"Current: -- Federal": {"2019": 39.5, "2018": 35.0, "2017": 10.4}, "Current: -- State": {"2019": 9.7, "2018": 9.4, "2017": 5.3}, "Current: -- Foreign": {"2019": 0.9, "2018": 0.8, "2017": 0.9}, "Current: -- Total current": {"2019": 50.1, "2018": 45.2, "2017": 16.6}, "Deferred: -- Federal": {"2019": -0.2, "2018": -2.3, "2017": -87.5}, "Deferred: -- State": {"2019": -8.0, "2018": -5.2, "2017": 9.1}, "Deferred: -- Total deferred": {"2019": -8.2, "2018": -7.5, "2017": -78.4}, "Deferred: -- Total income tax expense (benefit)": {"2019": 41.9, "2018": 37.7, "2017": -61.8}}
total_income_tax_expense_2019 = df["Deferred: -- Total income tax expense (benefit)"]["2019"]
total_income_tax_expense_2018 = df["Deferred: -- Total income tax expense (benefit)"]["2018"]
answer = total_income_tax_expense_2019 - total_income_tax_expense_2018