Trade Accounts Receivable

Additions to the allowances for doubtful accounts are recorded in other operating expenses. The following table presents the roll-forward of the allowance for doubtful accounts:

The exposure to credit risk at December 31, 2015 and 2014 was as follows:

As of December 31, 2015 and 2014, respectively, there was no indication that trade accounts receivable which were neither written-down nor past due could not be collected.