Costco Wholesale Corporation reported sales results for the month December 2016 and eighteen weeks ended January 1, 2017. For the month, net sales were $13.07 billion, the five weeks ended January 1, 2017, an increase of 5% from $12.46 billion during the similar period last year. For the eighteen weeks ended January 1, 2017, the company reported net sales of $43.18 billion, an increase of 4% from $41.66 billion during the similar period last year.