What was the percentage change in interest income in 2019 from 2018?
{"Unrealized gains on company owned life insurance contracts and investments held in rabbi trusts": {"2019": 0.8, "2018": 1.5, "2017": 1.7}, "Interest income": {"2019": 0.1, "2018": 0.3, "2017": 0.3}, "Foreign exchange": {"2019": -0.4, "2018": -0.7, "2017": -0.4}, "Pension earnings, interest and deferrals": {"2019": -0.1, "2018": -2.1, "2017": -23.8}, "Pension curtailment": {"2019": "\u2014", "2018": "\u2014", "2017": -0.5}, "Other": {"2019": 0.2, "2018": 0.2, "2017": 1.2}, "Total other income (expense), net": {"2019": 0.6, "2018": -0.8, "2017": -21.5}}
interest_income_2019 = df["Interest income"]["2019"]
interest_income_2018 = df["Interest income"]["2018"]
answer = ( interest_income_2019 - interest_income_2018 ) / interest_income_2018 * 100.0