Castle Company provides estimates for its uncollectible accounts. The allowance for uncollectible accounts had a credit balance of $17,880 at the beginning of 2016 and a $23,610 credit balance at the end of 2016 (after adjusting entries). If the direct write-off method had been used to account for uncollectible accounts (bad debt expense equals actual write-offs), the income statement for 2016 would have included bad debt expense of $18,300 and revenue of $3,400 from the collection of previously written off bad debts.

Required: Determine bad debt expense for 2016 according to the allowance method.