| | December 31, 2017 | | | December 31, 2016 | | ||
| | | | | | | ||
Balance at the beginning of the year | | Ps. | 6,824,935 | | | Ps. | 7,055,975 | |
Additions / Purchases (1) | | | 102,376 | | | | 2,805 | |
Foreign exchange adjustment | | | (26,255 | ) | | | (233,845 | ) |
Balance at the end of the year | | Ps. | 6,901,056 | | | Ps. | 6,824,935 | |