In addition to the $128.5 million of fee income earned through our third-party capital management activities described above, we earned $73.4 million of additional fees on other underwriting-related activities, primarily related to expense overrides paid to us by our reinsurers. These additional fees on other underwriting-related activities are recorded as a reduction to operating expenses or acquisition expenses, as applicable. The total fees recorded through underwriting income (loss) are detailed in the table below. Twelve months ended December 31 2021 2020 2019 (in thousands) Underwriting income (loss) - fee income on third-party capital management activities $ 67,287 $ 87,764 $ 60,046 Underwriting income (loss) - additional fees on other underwriting-related activities 73,418 59,080 47,828 Total fees recorded through underwriting income (loss) 140,705 146,844 107,874 Impact of Total fees recorded through underwriting income (loss) on the combined ratio 2.7 % 3.7 % 3.2 % Net Investment Income Year ended December 31, 2021 2020 2019 (in thousands) Fixed maturity investments $ 234,911 $ 278,215 $ 318,503 Short term investments 2,333 20,799 56,264 Equity investments trading 9,017 6,404 4,808 Other investments Catastrophe bonds 64,860 54,784 46,154 Other 28,811 9,417 8,447 Cash and cash equivalents 297 2,974 7,676 340,229 372,593 441,852 Investment expenses (20,750) (18,555) (17,645) Net investment income $ 319,479 $ 354,038 $ 424,207 Net investment income was $319.5 million in 2021, compared to $354.0 million in 2020, a decrease of $34.6 million. Impacting our net investment income for 2021 were lower returns in our fixed maturity and short term investment portfolios, primarily as a result of general decline in credit spreads and an increased allocation to lower yielding short term and U.S. treasury investments from other fixed maturity investments as compared to 2020. Net investment income was $354.0 million in 2020, compared to $424.2 million in 2019, a decrease of $70.2 million. Impacting our net investment income for 2020 was lower returns in our fixed maturity and short term investments, primarily as a result of lower yields on these investments following the decline in interest rates in early 2020, partially offset by higher returns on our catastrophe bonds due to growth in the portfolio. 84