CLB 2018 Annual Report

41 CORE LABORATORIES N.V. Schedule II - Valuation and Qualifying Account (In thousands) Balance at Beginning of Period Additions Charged to / Recovered from Expense Write-offs Other (1) Balance at End of Period Year ended December 31, 2018 Reserve for doubtful accounts $ 2,590 $ 605 $ (560) $ 15 $ 2,650 Year ended December 31, 2017 Reserve for doubtful accounts $ 3,139 $ (202) $ (428) $ 81 $ 2,590 Year ended December 31, 2016 Reserve for doubtful accounts $ 4,136 $ (18) $ (999) $ 20 $ 3,139 (1) Comprised primarily of differences due to changes in exchange rate.