Table:
|  | Year ended March 31, |  | Period-to-period change |  |
| --- | --- | --- | --- | --- |
| % Change | 2018 | 2017 | Amount | % Change |
|  |  | (dollars in thousands) |  |  |
| Other income (expense): |  |  |  |  |
| Interest income | $1,310 | $510 | $800 | 157% |
| Interest expense | (598) | (268) | (330) | 123% |
| Foreign exchange (expense) income and other, net | (3,439) | 6,892 | (10,331) | nm |
| Total other income (expense), net | $(2,727) | $7,134 | $(9,861) | nm |
Paragraphs:
Other income (expense)
nm—not meaningful
Other income (expense), net changed $9.9 million in the year ended March 31, 2018 compared to the year ended March 31, 2017, which was primarily attributable to a change of $10.4 million in foreign exchange expense which was primarily attributable to the re-measurement of short-term intercompany balances denominated in currencies other than the functional currency of our operating units. The increase in interest income is primarily due to interest on investments.
Question:
What caused the increase in interest income?
Answer: primarily due to interest on investments.