What was the percentage change in diluted net income per common share from 2018 to 2019?
{"Revenues": {"December 31, 2019": 2303737.0, "December 31, 2018": 2111373.0}, "Net income": {"December 31, 2019": 464602.0, "December 31, 2018": 442082.0}, "Net income per common share: -- Basic": {"December 31, 2019": 2.73, "December 31, 2018": 2.36}, "Net income per common share: -- Diluted": {"December 31, 2019": 2.59, "December 31, 2018": 2.3}}
net_income_2019 = df["Net income per common share: -- Diluted"]["December 31, 2019"]
net_income_2018 = df["Net income per common share: -- Diluted"]["December 31, 2018"]
answer = (net_income_2019 - net_income_2018) / net_income_2018 * 100.0