What was the percentage change in the total stock-based compensation expense between 2018 and 2019?
{"Restricted stock units": {"2019": 53766, "2018": 84082, "2017": 42122}, "Employee stock purchase plan (1)": {"2019": 7580, "2018": 6891, "2017": 6334}, "Other": {"2019": "\u2014", "2018": 7538, "2017": 88}, "Total": {"2019": 61346, "2018": 98511, "2017": 48544}}
total_2019 = df["Total"]["2019"]
total_2018 = df["Total"]["2018"]
answer = ( total_2019 - total_2018 ) / total_2018 * 100.0