What is the increase / (decrease) in revenue from 2018 to 2019?
{"($ in millions except per share amounts) -- For the year ended December 31:": {"2019": 2019.0, "2018": 2018.0}, "($ in millions except per share amounts) -- Revenue": {"2019": 77147.0, "2018": 79591.0}, "($ in millions except per share amounts) -- Net Income": {"2019": 9431.0, "2018": 8728.0}, "($ in millions except per share amounts) -- Income from continuing operations": {"2019": 9435.0, "2018": 8723.0}, "($ in millions except per share amounts) -- Operating (non-GAAP) earnings**": {"2019": 11436.0, "2018": 12657.0}, "Earnings per share of common stockcontinuing operations -- Assuming dilution": {"2019": 10.57, "2018": 9.51}, "Earnings per share of common stockcontinuing operations -- Basic": {"2019": 10.63, "2018": 9.56}, "Earnings per share of common stockcontinuing operations -- Diluted operating (non-GAAP)**": {"2019": 12.81, "2018": 13.81}, "Earnings per share of common stockcontinuing operations -- Net cash provided by operating activities": {"2019": 14770.0, "2018": 15247.0}, "Earnings per share of common stockcontinuing operations -- Capital expenditures, net": {"2019": 2370.0, "2018": 3716.0}, "Earnings per share of common stockcontinuing operations -- Share repurchases": {"2019": 1361.0, "2018": 4443.0}, "Earnings per share of common stockcontinuing operations -- Cash dividends paid on common stock": {"2019": 5707.0, "2018": 5666.0}, "Earnings per share of common stockcontinuing operations -- Per share of common stock": {"2019": 6.43, "2018": 6.21}, "Earnings per share of common stockcontinuing operations -- At December 31:": {"2019": 2019.0, "2018": 2018.0}, "Earnings per share of common stockcontinuing operations -- Cash, cash equivalents, restricted cash and marketable securities": {"2019": 9009.0, "2018": 12222.0}, "Earnings per share of common stockcontinuing operations -- Total assets": {"2019": 152186.0, "2018": 123382.0}, "Earnings per share of common stockcontinuing operations -- Working capital": {"2019": 718.0, "2018": 10918.0}, "Earnings per share of common stockcontinuing operations -- Total debt": {"2019": 62899.0, "2018": 45812.0}, "Earnings per share of common stockcontinuing operations -- Total equity": {"2019": 20985.0, "2018": 16929.0}, "Earnings per share of common stockcontinuing operations -- Common shares outstanding (in millions)": {"2019": 887.0, "2018": 892.0}, "Earnings per share of common stockcontinuing operations -- Stock price per common share": {"2019": 134.04, "2018": 113.67}}
revenue_2019 = df["($ in millions except per share amounts) -- Revenue"]["2019"]
revenue_2018 = df["($ in millions except per share amounts) -- Revenue"]["2018"]
answer = revenue_2019 - revenue_2018