What was the percentage change in the Total stock-based compensation expense between 2018 and 2019?
{"Stock options and assumed options": {"2019": 3783, "2018": 3511, "2017": 3913}, "Restricted stock units": {"2019": 16627, "2018": 9770, "2017": 3366}, "Restricted stock awards": {"2019": "\u2014", "2018": 1, "2017": 19}, "Employee stock purchase plan": {"2019": 193, "2018": 147, "2017": 115}, "Total stock-based compensation expense": {"2019": 20603, "2018": 13429, "2017": 7413}, "Tax benefit from stock-based awards": {"2019": 5154, "2018": 7581, "2017": 12719}}
total_stockbased_compensation_expense_2019 = df["Total stock-based compensation expense"]["2019"]
total_stockbased_compensation_expense_2018 = df["Total stock-based compensation expense"]["2018"]
answer = (total_stockbased_compensation_expense_2019 - total_stockbased_compensation_expense_2018) / total_stockbased_compensation_expense_2018 * 100.0