What is the percentage change in the net income available to common shareholders between 2018 and 2019?
{"Weighted average common shares outstanding": {"2019 Basic": 597961.0, "2018 Basic": 660925.0}, "Net income available to common shareholders": {"2019 Basic": 3202943.0, "2018 Basic": 3614610.0}, "Net earnings per share available to common shareholders": {"2019 Basic": 5.36, "2018 Basic": 5.47}}
net_income_2019 = df["Net income available to common shareholders"]["2019 Basic"]
net_income_2018 = df["Net income available to common shareholders"]["2018 Basic"]
answer = (net_income_2019 - net_income_2018) / net_income_2018 * 100.0