27. | Revenue |
| | For the years ended December 31, | | |||||||
| | 2017 | | 2016 | | 2015 | | |||
| | (in thousands) | | |||||||
Sale of goods | | $ | 329,584,136 | | | 318,243,539 | | | 351,566,289 | |
Other operating revenue | | | 11,444,131 | | | 10,845,497 | | | 8,780,205 | |
| | $ | 341,028,267 | | | 329,089,036 | | | 360,346,494 | |