What is the percentage change in the revenue earned from perpetual license between 2018 and 2019?
{"Revenue: -- Perpetual license": {"2019": 80015.0, "2018": 109863.0, "2017": 132883.0, "2016": 145053.0, "2015": 166305.0}, "Revenue: -- Term license": {"2019": 199433.0, "2018": 178256.0, "2017": 206411.0, "2016": 152231.0, "2015": 109283.0}, "Revenue: -- Maintenance": {"2019": 280580.0, "2018": 263875.0, "2017": 242320.0, "2016": 218635.0, "2015": 202802.0}, "Revenue: -- Cloud": {"2019": 133746.0, "2018": 82627.0, "2017": 51097.0, "2016": 40647.0, "2015": 30626.0}, "Revenue: -- Consulting": {"2019": 217609.0, "2018": 256960.0, "2017": 255756.0, "2016": 205663.0, "2015": 173679.0}, "Revenue: -- Total revenue": {"2019": 911383.0, "2018": 891581.0, "2017": 888467.0, "2016": 762229.0, "2015": 682695.0}, "Revenue: -- (Loss) income from operations": {"2019": -134878.0, "2018": -17032.0, "2017": 93177.0, "2016": 50644.0, "2015": 64661.0}, "Revenue: -- Net (loss) income": {"2019": -90433.0, "2018": 10617.0, "2017": 98548.0, "2016": 45015.0, "2015": 36322.0}, "(Loss) earnings per share -- Basic": {"2019": -1.14, "2018": 0.14, "2017": 1.27, "2016": 0.59, "2015": 0.47}, "(Loss) earnings per share -- Diluted": {"2019": -1.14, "2018": 0.13, "2017": 1.19, "2016": 0.56, "2015": 0.46}, "(Loss) earnings per share -- Cash dividends declared per common share": {"2019": 0.12, "2018": 0.12, "2017": 0.12, "2016": 0.12, "2015": 0.12}}
revenue_2019 = df["Revenue: -- Perpetual license"]["2019"]
revenue_2018 = df["Revenue: -- Perpetual license"]["2018"]
answer = (revenue_2019 - revenue_2018) / revenue_2018 * 100.0