| | 2017 | | 2016 | | 2015 | | |||
Balance as of January 1 | | $ | (97,400) | | | (81,641) | | | (76,793) | |
Increase in allowance | | | (14,800) | | | (18,405) | | | (17,179) | |
Amounts written off | | | 15,287 | | | 2,818 | | | 12,454 | |
Currency translation effect | | | 13 | | | (172) | | | (123) | |
Balance as of December 31, | | $ | (96,900) | | | (97,400) | | | (81,641) | |