What is the percentage change in diluted earnings per share for Class A common stock from the year ended December 31, 2018, to 2019?
{"Distributed earnings": {"2019": 43207.0, "2018": 39627.0, "2017": 32709.0}, "Undistributed earnings": {"2019": 70683.0, "2018": 42470.0, "2017": 81432.0}, "Net income": {"2019": 113890.0, "2018": 82097.0, "2017": 114141.0}, "Class A common stock: -- Basic net income available to common stockholders": {"2019": 76294.0, "2018": 54715.0, "2017": 75413.0}, "Class A common stock: -- Basic weighted average common shares outstanding": {"2019": 26763.0, "2018": 26354.0, "2017": 25685.0}, "Class A common stock: -- Basic earnings per share": {"2019": 2.85, "2018": 2.08, "2017": 2.94}, "Class A common stock: -- Diluted net income available to common stockholders": {"2019": 76555.0, "2018": 54937.0, "2017": 75698.0}, "Class A common stock: -- Effect of potential exercise of stock options": {"2019": 279.0, "2018": 324.0, "2017": 288.0}, "Class A common stock: -- Diluted weighted average common shares outstanding": {"2019": 27042.0, "2018": 26678.0, "2017": 25973.0}, "Class A common stock: -- Diluted earnings per share": {"2019": 2.83, "2018": 2.06, "2017": 2.91}, "Class B common stock: -- Basic net income available to common stockholders": {"2019": 37596.0, "2018": 27382.0, "2017": 38728.0}, "Class B common stock: -- Basic weighted average common shares outstanding": {"2019": 13188.0, "2018": 13189.0, "2017": 13190.0}, "Class B common stock: -- Basic earnings per share": {"2019": 2.85, "2018": 2.08, "2017": 2.94}, "Class B common stock: -- Diluted net income available to common stockholders": {"2019": 37335.0, "2018": 27160.0, "2017": 38443.0}, "Class B common stock: -- Diluted weighted average common shares outstanding": {"2019": 13188.0, "2018": 13189.0, "2017": 13190.0}, "Class B common stock: -- Diluted earnings per share": {"2019": 2.83, "2018": 2.06, "2017": 2.91}}
diluted_earnings_per_share_2019 = df["Class A common stock: -- Diluted earnings per share"]["2019"]
diluted_earnings_per_share_2018 = df["Class A common stock: -- Diluted earnings per share"]["2018"]
answer = ( diluted_earnings_per_share_2019 - diluted_earnings_per_share_2018 ) / diluted_earnings_per_share_2018 * 100.0