What was the percentage change in income tax benefit in 2019 from 2018?
{"Stock-based compensation (expense) (1)": {"2019": -7396, "2018": -7543, "2017": -7621}, "Income tax benefit (2)": {"2019": 1775, "2018": 1810, "2017": 2858}}
income_tax_2019 = df["Income tax benefit (2)"]["2019"]
income_tax_2018 = df["Income tax benefit (2)"]["2018"]
answer = (income_tax_2019 - income_tax_2018) / income_tax_2018 * 100.0