What was the change in pro forma net income between 2018 and 2019?
{"Pro forma revenue": {"2019": 1382957.0, "2018": 1361729.0}, "Pro forma net income": {"2019": 82003.0, "2018": 88428.0}, "Pro forma income per share: -- Basic": {"2019": 0.71, "2018": 0.76}, "Pro forma income per share: -- Diluted": {"2019": 0.69, "2018": 0.75}}
pro_forma_net_income_2019 = df["Pro forma net income"]["2019"]
pro_forma_net_income_2018 = df["Pro forma net income"]["2018"]
answer = pro_forma_net_income_2019 - pro_forma_net_income_2018