What is the percentage change in the income tax expense from 2018 to 2019?
{"September 30, 2019": {"Balance at Beginning of Year": 104858, "Income Tax Expense (Benefit)": 10448, "Reversal for State NOL Expiration and Utilization": -68292, "Balance at End of Year": 47014}, "September 30, 2018": {"Balance at Beginning of Year": 159154, "Income Tax Expense (Benefit)": 79377, "Reversal for State NOL Expiration and Utilization": -133673, "Balance at End of Year": 104858}, "September 30, 2017": {"Balance at Beginning of Year": 322404, "Income Tax Expense (Benefit)": -32154, "Reversal for State NOL Expiration and Utilization": -131096, "Balance at End of Year": 159154}}
income_tax_expense_2019 = df["September 30, 2019"]["Income Tax Expense (Benefit)"]
income_tax_expense_2018 = df["September 30, 2018"]["Income Tax Expense (Benefit)"]
answer = ( income_tax_expense_2019 - income_tax_expense_2018 ) / income_tax_expense_2018 * 100.0