What was the percentage change in nonvested RSUs between 2018 and 2019?
{"Nonvested as of December 31, 2018": {"Number of Shares": 651045.0, "Weighted Average Grant Date Fair Value": 23.82}, "Granted": {"Number of Shares": 742579.0, "Weighted Average Grant Date Fair Value": 33.28}, "Vested": {"Number of Shares": -259634.0, "Weighted Average Grant Date Fair Value": 24.16}, "Forfeited": {"Number of Shares": -124586.0, "Weighted Average Grant Date Fair Value": 29.79}, "Nonvested as of December 31, 2019": {"Number of Shares": 1009404.0, "Weighted Average Grant Date Fair Value": 29.96}}
nonvested_2019 = df["Nonvested as of December 31, 2019"]["Number of Shares"]
nonvested_2018 = df["Nonvested as of December 31, 2018"]["Number of Shares"]
answer = (nonvested_2019 - nonvested_2018) / nonvested_2018 * 100.0