What is the percentage change in the allowance for deferred tax assets at the end of period between 2018 and 2019?
{"Allowance for doubtful accounts -- 2019": {"Balance at Beginning of Period": 1.0, "": 1.0, "Write-offs": -0.8, "Other": 0.0, "Balance at End of Period": 1.2}, "Allowance for doubtful accounts -- 2018": {"Balance at Beginning of Period": 1.1, "": 0.7, "Write-offs": -0.8, "Other": 0.0, "Balance at End of Period": 1.0}, "Allowance for doubtful accounts -- 2017": {"Balance at Beginning of Period": 9.1, "": 1.0, "Write-offs": -0.9, "Other": 0.0, "Balance at End of Period": 1.1}, "Allowance for sales returns (4) -- 2019": {"Balance at Beginning of Period": 0.0, "": 0.0, "Write-offs": 0.0, "Other": 0.0, "Balance at End of Period": 0.0}, "Allowance for sales returns (4) -- 2018": {"Balance at Beginning of Period": 0.0, "": 0.0, "Write-offs": 0.0, "Other": 0.0, "Balance at End of Period": 0.0}, "Allowance for sales returns (4) -- 2017": {"Balance at Beginning of Period": 1.4, "": 1.4, "Write-offs": 0.0, "Other": -1.4, "Balance at End of Period": 1.4}, "Allowance for inventory returns (5) -- 2019": {"Balance at Beginning of Period": 0.0, "": 0.0, "Write-offs": 0.0, "Other": 0.0, "Balance at End of Period": 0.0}, "Allowance for inventory returns (5) -- 2018": {"Balance at Beginning of Period": 0.0, "": 0.0, "Write-offs": 0.0, "Other": 0.0, "Balance at End of Period": 0.0}, "Allowance for inventory returns (5) -- 2017": {"Balance at Beginning of Period": -0.6, "": -0.5, "Write-offs": 0.0, "Other": 0.6, "Balance at End of Period": -0.5}, "Allowance for deferred tax assets -- 2019": {"Balance at Beginning of Period": 18.3, "": -0.3, "Write-offs": 0.0, "Other": -1.2, "Balance at End of Period": 16.8}, "Allowance for deferred tax assets -- 2018": {"Balance at Beginning of Period": 18.3, "": -0.3, "Write-offs": 0.0, "Other": 0.3, "Balance at End of Period": 18.3}, "Allowance for deferred tax assets -- 2017": {"Balance at Beginning of Period": 69.0, "": -28.6, "Write-offs": -2.9, "Other": -19.2, "Balance at End of Period": 18.3}}
allowance_2019 = df["Allowance for deferred tax assets -- 2019"]["Balance at End of Period"]
allowance_2018 = df["Allowance for deferred tax assets -- 2018"]["Balance at End of Period"]
answer = ( allowance_2019 - allowance_2018 ) / allowance_2018 * 100.0