What was the increase / (decrease) in the Adjusted EBITDA margin from three months ended August 31, 2018 to 2019?
{"(in thousands of dollars, except percentages)": {"2019 (1)": "$", "2018 (2)": "$", "Change": "%", "Change in constant currency": "%", "Foreign exchange impact": "$"}, "Revenue": {"2019 (1)": 583673.0, "2018 (2)": 566184.0, "Change": 3.1, "Change in constant currency": 2.7, "Foreign exchange impact": 2427.0}, "Operating expenses": {"2019 (1)": 302833.0, "2018 (2)": 297977.0, "Change": 1.6, "Change in constant currency": 1.1, "Foreign exchange impact": 1441.0}, "Management fees  Cogeco Inc.": {"2019 (1)": 5230, "2018 (2)": 4796, "Change": 9.0, "Change in constant currency": 9.0, "Foreign exchange impact": "-"}, "Adjusted EBITDA": {"2019 (1)": 275610.0, "2018 (2)": 263411.0, "Change": 4.6, "Change in constant currency": 4.3, "Foreign exchange impact": 986.0}, "Adjusted EBITDA margin": {"2019 (1)": 47.2, "2018 (2)": 46.5, "Change": "", "Change in constant currency": "", "Foreign exchange impact": ""}}
adjusted_ebitda_margin_2019_1 = df["Adjusted EBITDA margin"]["2019 (1)"]
adjusted_ebitda_margin_2018_2 = df["Adjusted EBITDA margin"]["2018 (2)"]
answer = adjusted_ebitda_margin_2019_1 - adjusted_ebitda_margin_2018_2