What was the percentage change in the amount Expiring after the following year in 2019 from 2018?
{"Unused tax losses -- Not expiring": {"2019": 688, "2018": 575, "2017": 375}, "Unused tax losses -- Expiring in the following year": {"2019": 63, "2018": 7, "2017": 9}, "Unused tax losses -- Expiring after the following year": {"2019": 373, "2018": 476, "2017": 535}, "Unused tax losses -- Total unused tax losses": {"2019": 1124, "2018": 1058, "2017": 919}, "Unused tax losses -- Deductible temporary differences": {"2019": 538, "2018": 509, "2017": 524}, "Unused research and development and foreign tax credits -- Not expiring": {"2019": 28, "2018": 54, "2017": 38}, "Unused research and development and foreign tax credits -- Expiring in the following year": {"2019": 0, "2018": 0, "2017": 2}, "Unused research and development and foreign tax credits -- Expiring after the following year": {"2019": 17, "2018": 18, "2017": 34}, "Unused research and development and foreign tax credits -- Total unused tax credits": {"2019": 45, "2018": 72, "2017": 74}}
exp_2019 = df["Unused research and development and foreign tax credits -- Expiring after the following year"]["2019"]
exp_2018 = df["Unused research and development and foreign tax credits -- Expiring after the following year"]["2018"]
answer = (exp_2019 - exp_2018) / exp_2018 * 100.0