| December 31, 2017 | December 31, 2016 |
In millions of COP | ||
Balance at beginning of the year, net | 6,130,095 | 6,484,669 |
Effect of change in foreign exchange rate | (34,136) | (354,574) |
Balance at end of the year, net | 6,095,959 | 6,130,095 |