What was the percentage change in adjusted EBITDA between 2018 and 2019?
{"Other Financial and Operating Data: -- SaaS and license revenue renewal rate(3)": {"2019": 94, "2018": 93, "2017": 93, "2016": 94, "2015": 93}, "Other Financial and Operating Data: -- Adjusted EBITDA(4)": {"2019": 108307, "2018": 93081, "2017": 71628, "2016": 49034, "2015": 34370}}
adjusted_ebitda_2019 = df["Other Financial and Operating Data: -- Adjusted EBITDA(4)"]["2019"]
adjusted_ebitda_2018 = df["Other Financial and Operating Data: -- Adjusted EBITDA(4)"]["2018"]
answer = (adjusted_ebitda_2019 - adjusted_ebitda_2018) / adjusted_ebitda_2018 * 100.0