What is the percentage change in revenue between 2018 and 2019?
{"For the Years Ended December 31, -- ": {"2019": 2019.0, "2018": 2018.0, "Change": "Change", "% Change": "% Change"}, "(In millions, except percentages) -- Revenues": {"2019": 13.2, "2018": 82.3, "Change": -69.1, "% Change": -84.0}, "(In millions, except percentages) -- Cost of revenues": {"2019": 1.9, "2018": 15.3, "Change": -13.4, "% Change": -88.0}, "(In millions, except percentages) -- Gross profit": {"2019": 11.3, "2018": 67.0, "Change": -55.7, "% Change": -83.0}, "(In millions, except percentages) -- Gross margin": {"2019": 86.0, "2018": 81.0, "Change": "", "% Change": ""}, "Operating expenses: -- Selling, general and administrative": {"2019": 31.7, "2018": 32.2, "Change": -0.5, "% Change": -2.0}, "Operating expenses: -- Research and development": {"2019": 2.0, "2018": 2.1, "Change": -0.1, "% Change": -5.0}, "Operating expenses: -- Total operating expenses": {"2019": 33.7, "2018": 34.3, "Change": -0.6, "% Change": -2.0}, "Operating expenses: -- Other expense": {"2019": -0.3, "2018": -4.0, "Change": 3.7, "% Change": -93.0}, "Operating expenses: -- Income (loss) before income taxes": {"2019": -22.7, "2018": 28.7, "Change": -51.4, "% Change": -179.0}, "Operating expenses: -- Income tax provision (benefit)": {"2019": -6.2, "2018": 8.0, "Change": -14.2, "% Change": -178.0}, "Operating expenses: -- Net income (loss)": {"2019": -16.5, "2018": 20.7, "Change": -37.2, "% Change": -180.0}}
revenue_2019 = df["(In millions, except percentages) -- Revenues"]["2019"]
revenue_2018 = df["(In millions, except percentages) -- Revenues"]["2018"]
answer = (revenue_2019 - revenue_2018) / revenue_2018 * 100.0