What is the percentage change in adjusted gross profit from 2018 to 2019?
{"": {"2019": "(Dollars in thousands)", "2018": "", "2017": "", "2016": "", "2015": ""}, "Gross Profit": {"2019": 114197, "2018": 89990, "2017": 72416, "2016": 60371, "2015": 54649}, "Depreciation expense (a)": {"2019": 6370, "2018": 6089, "2017": 5791, "2016": 4028, "2015": 2566}, "Plant start-up expense (b)": {"2019": "\u2014", "2018": "\u2014", "2017": "\u2014", "2016": 1628, "2015": "\u2014"}, "Non-cash share-based compensation (c)": {"2019": 922, "2018": 859, "2017": 243, "2016": 221, "2015": 201}, "Adjusted Gross Profit": {"2019": 121489, "2018": 96938, "2017": 78450, "2016": 66248, "2015": 57416}, "Adjusted Gross Profit as a % of Net Sales": {"2019": 49.4, "2018": 50.2, "2017": 51.5, "2016": 51.1, "2015": 50.6}}
adjusted_gross_profit_2019 = df["Adjusted Gross Profit"]["2019"]
adjusted_gross_profit_2018 = df["Adjusted Gross Profit"]["2018"]
answer = (adjusted_gross_profit_2019 - adjusted_gross_profit_2018) / adjusted_gross_profit_2018 * 100.0