What is the change in Allowance for doubtful accounts between 2019 and 2018?
{"Deferred tax assets -- Accruals and reserves, net": {"2019": 29627, "2018": 31565}, "Deferred tax assets -- Allowance for doubtful accounts": {"2019": 11507, "2018": 11378}, "Deferred tax assets -- Stock-based compensation, net": {"2019": 10382, "2018": 10595}, "Deferred tax assets -- Deferred revenue": {"2019": 21786, "2018": 8160}, "Deferred tax assets -- Operating and finance lease liabilities": {"2019": 22085, "2018": 0}, "Deferred tax assets -- Net operating loss carryforwards": {"2019": 37717, "2018": 36649}, "Deferred tax assets -- Research and development tax credit": {"2019": 899, "2018": 899}, "Deferred tax assets -- Other": {"2019": 7488, "2018": 10784}, "Deferred tax assets -- Less:  Valuation Allowance": {"2019": -19219, "2018": -18734}, "Deferred tax assets -- Total deferred tax assets": {"2019": 122272, "2018": 91296}, "Deferred tax liabilities -- Prepaid expense": {"2019": -5372, "2018": -6733}, "Deferred tax liabilities -- Property and equipment, net": {"2019": -3695, "2018": -7442}, "Deferred tax liabilities -- Acquired intangibles, net": {"2019": -111284, "2018": -129879}, "Deferred tax liabilities -- Operating and finance right-to-use assets": {"2019": -17255, "2018": 0}, "Deferred tax liabilities -- Other": {"2019": 0, "2018": -676}, "Deferred tax liabilities -- Total deferred tax liabilities": {"2019": -137606, "2018": -144730}, "Deferred tax liabilities -- Net deferred tax liabilities": {"2019": -15334, "2018": -53434}}
allowance_for_doubtful_accounts_2019 = df["Deferred tax assets -- Allowance for doubtful accounts"]["2019"]
allowance_for_doubtful_accounts_2018 = df["Deferred tax assets -- Allowance for doubtful accounts"]["2018"]
answer = allowance_for_doubtful_accounts_2019 - allowance_for_doubtful_accounts_2018