pre_text: Other Income (Expense) Interest income in 2019 increased by $0.4 million due to an increase in interest income earned on investment securities and money market portfolios. Interest expense in 2019 decreased by $6.6 million due to the payoff of the 1.50% convertible notes due July 1, 2018 with a principal amount of $253.0 million (the “2018 Notes”) in the third quarter of 2018. Refer to the section titled “Liquidity and Capital Resources” for additional information on the convertible notes. Other, net primarily included foreign exchange gains and losses related to transactions denominated in foreign currencies, as well as foreign exchange gains and losses related to our intercompany loans and certain cash accounts. Foreign exchange gains and losses for the years ended December 31, 2019, 2018, and 2017, were primarily driven by fluctuations in the euro and US dollar in relation to the British pound.
table: Year Ended December 31,
table: 2019 2018 2017
table: (in thousands)
table: Interest income $8,178 $7,796 $2,951
table: Interest expense (21,559) (28,176) (14,762)
table: Other, net 84 (3,098) 1,478
table: Other expense, net $(13,297) $(23,478) $(10,333)
question: Analyse this data from a financial earnings document. What is the average interest income from 2017-2019?