What was the average revenue in 2019 and 2018?
{"Orders": {"2019": 15944.0, "2018": 16287.0, "Actual": -2.0, "Comp.": -4.0}, "Revenue": {"2019": 16087.0, "2018": 15587.0, "Actual": 3.0, "Comp.": 2.0}, "therein: software business": {"2019": 4039.0, "2018": 3560.0, "Actual": 13.0, "Comp.": 8.0}, "Adjusted EBITA": {"2019": 2880.0, "2018": 2898.0, "Actual": -1, "Comp.": ""}, "Adjusted EBITA margin": {"2019": 17.9, "2018": 18.6, "Actual": "", "Comp.": ""}}
revenue_2019 = df["Revenue"]["2019"]
revenue_2018 = df["Revenue"]["2018"]
revenue_comp = df["Revenue"]["Comp."]
answer = ( revenue_2019 + revenue_2018 ) / revenue_comp