What is the increase / (decrease) in the Adjusted EBITDA margin from 2018 to 2019?
{"Orders": {"2019": 12894.0, "2018": 11025.0, "Actual": 17.0, "Comp.": 16.0}, "Revenue": {"2019": 8916.0, "2018": 8821.0, "Actual": 1.0, "Comp.": 0.0}, "Adjusted EBITA": {"2019": 983.0, "2018": 958.0, "Actual": 3, "Comp.": ""}, "Adjusted EBITA margin": {"2019": 11.0, "2018": 10.9, "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