What was the percentage change in balances at end of period between 2018 and 2019?
{"Balances at beginning of period": {"2019": 2084, "2018": 2312, "2017": 2329}, "Warranty acquired in business combinations": {"2019": 4818, "2018": 305, "2017": 118}, "Increases to accruals": {"2019": 1752, "2018": 1606, "2017": 2029}, "Warranty expenditures": {"2019": -2249, "2018": -2127, "2017": -2184}, "Effect of changes in exchange rates": {"2019": 8, "2018": -12, "2017": 20}, "Balances at end of period": {"2019": 6413, "2018": 2084, "2017": 2312}}
balances_2019 = df["Balances at end of period"]["2019"]
balances_2018 = df["Balances at beginning of period"]["2019"]
answer = ( balances_2019 - balances_2018 ) / balances_2018 * 100.0