What is the percentage change in revenue between 2018 and 2019?
{"Consolidated Statement of Operations Data -- Revenue": {"2019": 212628.0, "2018": 232223.0, "2017": 235429.0, "2016": 227297.0, "2015": 196285.0}, "Consolidated Statement of Operations Data -- Cost of revenue": {"2019": 48881.0, "2018": 51896.0, "2017": 53318.0, "2016": 54413.0, "2015": 48402.0}, "Consolidated Statement of Operations Data -- Gross profit": {"2019": 163747.0, "2018": 180327.0, "2017": 182111.0, "2016": 172884.0, "2015": 147883.0}, "Consolidated Statement of Operations Data -- Loss from operations": {"2019": -17094.0, "2018": -27679.0, "2017": -10372.0, "2016": -20570.0, "2015": -40309.0}, "Consolidated Statement of Operations Data -- Net loss": {"2019": -17819.0, "2018": -27617.0, "2017": -10751.0, "2016": -22391.0, "2015": -41897.0}, "Consolidated Statement of Operations Data -- Net loss per share: basic and diluted": {"2019": -0.23, "2018": -0.38, "2017": -0.15, "2016": -0.34, "2015": -0.67}, "Weighted-average shares used in computing net -- loss per share: basic and diluted": {"2019": 76080.0, "2018": 72882.0, "2017": 70053.0, "2016": 65701.0, "2015": 62428.0}, "Consolidated Balance Sheet Data: -- Cash,cash equivalents and marketable securities": {"2019": 129922.0, "2018": 128375.0, "2017": 131134.0, "2016": 114347.0, "2015": 98117.0}, "Consolidated Balance Sheet Data: -- Working capital": {"2019": 123358.0, "2018": 117572.0, "2017": 111076.0, "2016": 95285.0, "2015": 89550.0}, "Consolidated Balance Sheet Data: -- Total assets": {"2019": 274053.0, "2018": 235876.0, "2017": 224858.0, "2016": 216733.0, "2015": 189892.0}, "Consolidated Balance Sheet Data: -- Deferred revenue(current and non-current)": {"2019": 101164.0, "2018": 97966.0, "2017": 94637.0, "2016": 91617.0, "2015": 72008.0}, "Consolidated Balance Sheet Data: -- Total stockholders equity": {"2019": 108787.0, "2018": 103883.0, "2017": 98386.0, "2016": 82752.0, "2015": 78205.0}}
revenue_2019 = df["Consolidated Statement of Operations Data -- Revenue"]["2019"]
revenue_2018 = df["Consolidated Statement of Operations Data -- Revenue"]["2018"]
answer = (revenue_2019 - revenue_2018) / revenue_2018 * 100.0