What was the percentage change in the balances at beginning of period between 2018 and 2019?
{"Balances at beginning of period": {"2019": 1856, "2018": 1748}, "Additions from acquisition": {"2019": 1884, "2018": 416}, "Additions - charged to expense": {"2019": 4207, "2018": 109}, "Deductions - write-offs, net of recoveries": {"2019": -202, "2018": -417}, "Balances at end of period": {"2019": 7745, "2018": 1856}}
balances_2019 = df["Balances at beginning of period"]["2019"]
balances_2018 = df["Balances at beginning of period"]["2018"]
answer = ( balances_2019 - balances_2018 ) / balances_2018 * 100.0