What is the increase / (decrease) in the Adjusted EBITDA margin from 2018 to 2019?
{"Orders": {"2019": 15853.0, "2018": 14506.0, "Actual": 9.0, "Comp.": 7.0}, "Revenue": {"2019": 14517.0, "2018": 13425.0, "Actual": 8.0, "Comp.": 6.0}, "Adjusted EBITA": {"2019": 2461.0, "2018": 2221.0, "Actual": 11, "Comp.": ""}, "Adjusted EBITA margin": {"2019": 17.0, "2018": 16.5, "Actual": "", "Comp.": ""}}
adjusted_ebita_margin_2019 = df["Adjusted EBITA margin"]["2019"]
adjusted_ebita_margin_2018 = df["Adjusted EBITA margin"]["2018"]
answer = adjusted_ebita_margin_2019 - adjusted_ebita_margin_2018