What was the percentage change in segment adjusted EBITDA ACI on Premise between 2018 and 2019?
{"Revenues -- ACI On Premise": {"2019": 579334, "2018": 576755}, "Revenues -- ACI On Demand": {"2019": 678960, "2018": 433025}, "Revenues -- Total revenue": {"2019": 1258294, "2018": 1009780}, "Segment Adjusted EBITDA -- ACI On Premise": {"2019": 321305, "2018": 323902}, "Segment Adjusted EBITDA -- ACI On Demand": {"2019": 66501, "2018": 12015}, "Segment Adjusted EBITDA -- Depreciation and amortization": {"2019": -122569, "2018": -97350}, "Segment Adjusted EBITDA -- Stock-based compensation expense": {"2019": -36763, "2018": -20360}, "Segment Adjusted EBITDA -- Corporate and unallocated expenses": {"2019": -104718, "2018": -92296}, "Segment Adjusted EBITDA -- Interest, net": {"2019": -52066, "2018": -30388}, "Segment Adjusted EBITDA -- Other, net": {"2019": 520, "2018": -3724}, "Segment Adjusted EBITDA -- Income before income taxes": {"2019": 72210, "2018": 91799}, "Depreciation and amortization -- ACI On Premise": {"2019": 11992, "2018": 11634}, "Depreciation and amortization -- ACI On Demand": {"2019": 34395, "2018": 31541}, "Depreciation and amortization -- Corporate": {"2019": 76182, "2018": 54175}, "Depreciation and amortization -- Total depreciation and amortization": {"2019": 122569, "2018": 97350}, "Stock-based compensation expense -- ACI On Premise": {"2019": 7651, "2018": 4348}, "Stock-based compensation expense -- ACI On Demand": {"2019": 7995, "2018": 4338}, "Stock-based compensation expense -- Corporate and other": {"2019": 21117, "2018": 11674}, "Stock-based compensation expense -- Total stock-based compensation expense": {"2019": 36763, "2018": 20360}}
segment_adjusted_ebitda_aci_on_premise_2019 = df["Segment Adjusted EBITDA -- ACI On Premise"]["2019"]
segment_adjusted_ebitda_aci_on_premise_2018 = df["Segment Adjusted EBITDA -- ACI On Premise"]["2018"]
answer = ( segment_adjusted_ebitda_aci_on_premise_2019 - segment_adjusted_ebitda_aci_on_premise_2018 ) / segment_adjusted_ebitda_aci_on_premise_2018 * 100.0