What was the percentage change in Dilutive impact of share-based compensation arrangements in 2019 from 2018?
{"": {"2019": "", "2018": "(in millions)", "2017": ""}, "Basic": {"2019": 338, "2018": 350, "2017": 355}, "Dilutive impact of share-based compensation arrangements": {"2019": 2, "2018": 3, "2017": 3}, "Diluted": {"2019": 340, "2018": 353, "2017": 358}}
dilutive_impact_2019 = df["Dilutive impact of share-based compensation arrangements"]["2019"]
dilutive_impact_2018 = df["Dilutive impact of share-based compensation arrangements"]["2018"]
answer = (dilutive_impact_2019 - dilutive_impact_2018) / dilutive_impact_2018 * 100.0