What was the change in Valuation allowance for deferred tax assets between 2018 and 2019?
{"At December 31, 2019 -- Allowances for sales returns and price protection and other allowances": {"Col B. Balance at Beginning of Period": 186, "Col. C Additions(A)": 11, "Col. D Deductions(B)": -79, "Col. E Balance at End of Period": 118}, "At December 31, 2019 -- Valuation allowance for deferred tax assets": {"Col B. Balance at Beginning of Period": 61, "Col. C Additions(A)": 127, "Col. D Deductions(B)": -7, "Col. E Balance at End of Period": 181}, "At December 31, 2018 -- Allowances for sales returns and price protection and other allowances": {"Col B. Balance at Beginning of Period": 274, "Col. C Additions(A)": 24, "Col. D Deductions(B)": -112, "Col. E Balance at End of Period": 186}, "At December 31, 2018 -- Valuation allowance for deferred tax assets": {"Col B. Balance at Beginning of Period": "$\u2014", "Col. C Additions(A)": 61, "Col. D Deductions(B)": "$\u2014", "Col. E Balance at End of Period": 61}, "At December 31, 2017 -- Allowances for sales returns and price protection and other allowances": {"Col B. Balance at Beginning of Period": 257, "Col. C Additions(A)": 83, "Col. D Deductions(B)": -66, "Col. E Balance at End of Period": 274}}
valuation_allowance_2019 = df["At December 31, 2019 -- Valuation allowance for deferred tax assets"]["Col. E Balance at End of Period"]
valuation_allowance_2018 = df["At December 31, 2019 -- Valuation allowance for deferred tax assets"]["Col B. Balance at Beginning of Period"]
answer = valuation_allowance_2019 - valuation_allowance_2018