What was the change in the basic net income per common share in 2019 from 2018?
{"Income Statement Data (3): -- Revenues": {"2019 (1)": 1614762.0, "2018 (2)": 1625687.0, "2017": 1586008.0, "2016": 1460037.0, "2015": 1286340.0}, "Income Statement Data (3): -- Income from operations (4)(5)": {"2019 (1)": 89800.0, "2018 (2)": 63202.0, "2017": 87042.0, "2016": 92373.0, "2015": 94358.0}, "Income Statement Data (3): -- Net income (4)(5)(6)": {"2019 (1)": 64081.0, "2018 (2)": 48926.0, "2017": 32216.0, "2016": 62390.0, "2015": 68597.0}, "Net Income Per Common Share: (3)(4)(5)(6) -- Basic": {"2019 (1)": 1.54, "2018 (2)": 1.16, "2017": 0.77, "2016": 1.49, "2015": 1.64}, "Net Income Per Common Share: (3)(4)(5)(6) -- Diluted": {"2019 (1)": 1.53, "2018 (2)": 1.16, "2017": 0.76, "2016": 1.48, "2015": 1.62}, "Weighted Average Common Shares: -- Basic": {"2019 (1)": 41649.0, "2018 (2)": 42090.0, "2017": 41822.0, "2016": 41847.0, "2015": 41899.0}, "Weighted Average Common Shares: -- Diluted": {"2019 (1)": 41802.0, "2018 (2)": 42246.0, "2017": 42141.0, "2016": 42239.0, "2015": 42447.0}, "Balance Sheet Data: (3)(4)(6)(7) -- Total assets": {"2019 (1)": 1415500.0, "2018 (2)": 1171967.0, "2017": 1327092.0, "2016": 1236403.0, "2015": 947772.0}, "Balance Sheet Data: (3)(4)(6)(7) -- Long-term debt": {"2019 (1)": 73000.0, "2018 (2)": 102000.0, "2017": 275000.0, "2016": 267000.0, "2015": 70000.0}, "Balance Sheet Data: (3)(4)(6)(7) -- Shareholders' equity": {"2019 (1)": 874475.0, "2018 (2)": 826609.0, "2017": 796479.0, "2016": 724522.0, "2015": 678680.0}}
net_income_per_common_share_2019 = df["Net Income Per Common Share: (3)(4)(5)(6) -- Basic"]["2019 (1)"]
net_income_per_common_share_2018 = df["Net Income Per Common Share: (3)(4)(5)(6) -- Basic"]["2018 (2)"]
answer = net_income_per_common_share_2019 - net_income_per_common_share_2018