What was the percentage change in Total stock-based compensation expense between 2018 and 2019?
{"Revenues -- ACI On Premise": {"2019": 579334, "2018": 576755, "2017": 598590}, "Revenues -- ACI On Demand": {"2019": 678960, "2018": 433025, "2017": 425601}, "Revenues -- Total revenue": {"2019": 1258294, "2018": 1009780, "2017": 1024191}, "Segment Adjusted EBITDA -- ACI On Premise": {"2019": 321305, "2018": 323902, "2017": 347094}, "Segment Adjusted EBITDA -- ACI On Demand": {"2019": 66501, "2018": 12015, "2017": -1832}, "Segment Adjusted EBITDA -- Depreciation and amortization": {"2019": -122569, "2018": -97350, "2017": -102224}, "Segment Adjusted EBITDA -- Stock-based compensation expense": {"2019": -36763, "2018": -20360, "2017": -13683}, "Segment Adjusted EBITDA -- Corporate and unallocated expenses": {"2019": -104718, "2018": -92296, "2017": -144715}, "Segment Adjusted EBITDA -- Interest, net": {"2019": -52066, "2018": -30388, "2017": -38449}, "Segment Adjusted EBITDA -- Other, net": {"2019": 520, "2018": -3724, "2017": -2619}, "Segment Adjusted EBITDA -- Income before income taxes": {"2019": 72210, "2018": 91799, "2017": 43572}, "Depreciation and amortization -- ACI On Premise": {"2019": 11992, "2018": 11634, "2017": 13094}, "Depreciation and amortization -- ACI On Demand": {"2019": 34395, "2018": 31541, "2017": 34171}, "Depreciation and amortization -- Corporate": {"2019": 76182, "2018": 54175, "2017": 54959}, "Depreciation and amortization -- Total depreciation and amortization": {"2019": 122569, "2018": 97350, "2017": 102224}, "Stock-based compensation expense -- ACI On Premise": {"2019": 7651, "2018": 4348, "2017": 2234}, "Stock-based compensation expense -- ACI On Demand": {"2019": 7995, "2018": 4338, "2017": 2230}, "Stock-based compensation expense -- Corporate": {"2019": 21117, "2018": 11674, "2017": 9219}, "Stock-based compensation expense -- Total stock-based compensation expense": {"2019": 36763, "2018": 20360, "2017": 13683}}
total_stockbased_compensation_expense_2019 = df["Stock-based compensation expense -- Total stock-based compensation expense"]["2019"]
total_stockbased_compensation_expense_2018 = df["Stock-based compensation expense -- Total stock-based compensation expense"]["2018"]
answer = (total_stockbased_compensation_expense_2019 - total_stockbased_compensation_expense_2018) / total_stockbased_compensation_expense_2018 * 100.0