What was the percentage change in dilutive effect of employee stock plans from 2017 to 2018?
{"Year Ended May 31, -- (in millions, except per share data)": {"2019": 2019.0, "2018": 2018.0, "2017": 2017.0}, "Year Ended May 31, -- Net income": {"2019": 11083.0, "2018": 3587.0, "2017": 9452.0}, "Year Ended May 31, -- Weighted average common shares outstanding": {"2019": 3634.0, "2018": 4121.0, "2017": 4115.0}, "Year Ended May 31, -- Dilutive effect of employee stock plans": {"2019": 98.0, "2018": 117.0, "2017": 102.0}, "Year Ended May 31, -- Dilutive weighted average common shares outstanding": {"2019": 3732.0, "2018": 4238.0, "2017": 4217.0}, "Year Ended May 31, -- Basic earnings per share": {"2019": 3.05, "2018": 0.87, "2017": 2.3}, "Year Ended May 31, -- Diluted earnings per share": {"2019": 2.97, "2018": 0.85, "2017": 2.24}, "Year Ended May 31, -- Shares subject to anti-dilutive restricted stock-based awards and stock options excluded from calculation (1)": {"2019": 71.0, "2018": 64.0, "2017": 74.0}}
dilutive_effect_2018 = df["Year Ended May 31, -- Dilutive effect of employee stock plans"]["2018"]
dilutive_effect_2017 = df["Year Ended May 31, -- Dilutive effect of employee stock plans"]["2017"]
answer = ( dilutive_effect_2018 - dilutive_effect_2017 ) / dilutive_effect_2017 * 100.0