Table:
|  |  | Years Ended |  | 2019 vs. 2018 |
| --- | --- | --- | --- | --- |
|  | July 27, 2019 | July 28, 2018 | July 29, 2017 | Variance in Dollars |
| Interest income | $1,308 | $1,508 | $1,338 | $(200) |
| Interest expense | (859) | (943) | (861) | 84 |
| Interest income (expense), net | $449 | $565 | $477 | $(116) |
Paragraphs:
Interest and Other Income (Loss), Net
Interest Income (Expense), Net The following table summarizes interest income and interest expense (in millions):
Interest income decreased, driven by a decrease in the average balance of cash and available-for-sale debt investments. The decrease in interest expense was driven by a lower average debt balance, partially offset by the impact of higher effective interest rates.
Question:
Why did interest income decrease?
Answer: driven by a decrease in the average balance of cash and available-for-sale debt investments.