What was the percentage change in the ending balance between 2017 and 2018?
{"Beginning balance": {"2019": 138589, "2018": 94148, "2017": 68064}, "Receipts(1)": {"2019": 159527, "2018": 129153, "2017": 109818}, "Settlements(2)": {"2019": -262449, "2018": -181590, "2017": -127029}, "Fair value changes recognized in cost of revenue(3)": {"2019": 170368, "2018": 96878, "2017": 43295}, "Ending balance": {"2019": 206035, "2018": 138589, "2017": 94148}}
beginning_balance_2019 = df["Beginning balance"]["2019"]
beginning_balance_2018 = df["Beginning balance"]["2018"]
answer = ( beginning_balance_2019 - beginning_balance_2018 ) / beginning_balance_2018 * 100.0