Table:
|  | Year Ended December 31, | Year Ended December 31, | Year Ended December 31, | % Variation | % Variation |
| --- | --- | --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 | 2019 vs 2018 | 2018 vs 2017 |
|  | (in millions) | (in millions) | (in millions) |  |  |
| Net sales | $9,529 | $9,612 | $8,308 | (0.9)% | 15.7% |
| Other revenues | 27 | 52 | 39 | (49.0) | 36.1 |
| Net revenues | $9,556 | $9,664 | $8,347 | (1.1)% | 15.8% |
Paragraphs:
Our 2019 net revenues decreased 1.1% compared to the prior year, primarily due to a decrease in volumes of approximately 8%, partially compensated by an increase in average selling prices of approximately 7%. The increase in the average selling prices was driven by favorable product mix of approximately 10%, partially offset by a negative pricing effect of approximately 3%.
Our 2018 net revenues increased 15.8% compared to the prior year, primarily due to increase in average selling prices of approximately 16%, while volumes remained substantially flat. The increase in the average selling prices was driven by favorable product mix of approximately 18%, partially offset by a negative pricing effect of approximately 2%. Our net revenues registered double-digit growth across all product groups and geographies.
In 2019, 2018 and 2017, our largest customer, Apple, accounted for 17.6%, 13.1% and 10.5% of our net revenues, respectively, reported within our three product groups.
Question:
Why did the 2018 net revenues increased 15.8% compared to the prior year?
Answer: increase in average selling prices of approximately 16%, while volumes remained substantially flat.