Table of Contents The following table details the results of operations for Specialty. Net written premiums for Specialty increased $13 million in 2018 as compared with 2017 driven by higher new business and positive renewal premium change partially offset by lower retention. The increase in net earned premiums was consistent with the trend in net written premiums. Core income increased $47 million in 2018 as compared with 2017. Excluding the favorable effect of the Federal corporate income tax rate change, core income decreased approximately $60 million due to lower net investment income driven by limited partnership returns and lower favorable net prior year loss reserve development partially offset by improved non-catastrophe current accident year underwriting results. The combined ratio of 88.2% improved 0.5 points in 2018 as compared with 2017. The loss ratio improved 0.6 points primarily due to an improved current accident year loss ratio partially offset by lower favorable net prior year loss reserve development. Net catastrophe losses were $26 million, or 1.0 points of the loss ratio, for 2018, as compared with $44 million, or 1.6 points of the loss ratio, for 2017. The expense ratio in 2018 was consistent with the same period in 2017. Favorable net prior year loss reserve development of $150 million and $174 million was recorded in 2018 and 2017. Further information on net prior year loss reserve development is in Note E to the Consolidated Financial Statements included under Item 8. 2018 Compared with 2017 32 Years ended December 31 (In millions, except ratios, rate, renewal premium change and retention) 2018 2017 2016 Net written premiums $ 2,744 $ 2,731 $ 2,738 Net earned premiums 2,732 2,712 2,743 Net investment income 439 522 497 Core income 629 582 606 Other performance metrics: Loss and loss adjustment expense ratio 55.9 % 56.5 % 54.3 % Expense ratio 32.1 32.0 32.1 Dividend ratio 0.2 0.2 0.2 Combined ratio 88.2% 88.7% 86.6% Rate 2% 1% 1% Renewal premium change 3 3 2 Retention 84 89 88 New business $ 353 $ 242 $ 239