Table:
|  |  | Fiscal Year Ended |  |
| --- | --- | --- | --- |
|  | December 28, 2019 | December 29, 2018 | December 30, 2017 |
|  |  | (Dollars in thousands) |  |
| Interest income | $2,714 | $1,356 | $548 |
| Weighted average balance of cash and investments | $179,526 | $138,467 | $124,637 |
| Weighted average yield on cash and investments | 2.05 % | 1.51 % | 0.84 % |
| Interest expense | $1,915 | $3,314 | $4,491 |
| Average debt outstanding | $56,776 | $90,086 | $127,598 |
| Weighted average interest rate on debt | 4.09 % | 3.98 % | 3.07 % |
Paragraphs:
Interest Income and Interest Expense
Interest income is earned on our cash, cash equivalents, restricted cash and marketable securities. The increase in interest income in fiscal 2019 compared to fiscal 2018 was attributable to higher investment yields, related in part to longer duration investments, as well as higher average investment balances.
Interest expense primarily includes interest on our term loans, partially offset by income from our interest-rate swap derivative contracts, as well as term loan issuance costs amortization charges. The decrease in interest expense in fiscal 2019 compared to fiscal 2018 was primarily due to lower outstanding debt balances related to the CMI acquisition as a result of principal payments made, partially offset by additional interest expense related to the term loan originated to finance the acquisition of FRT.
Other Income (Expense), Net
Other income (expense), net primarily includes the effects of foreign currency impact and various other gains and losses.
Question:
How is Interest income earned?
Answer: on our cash, cash equivalents, restricted cash and marketable securities.