results relative to the prior period. In periods when the functional currency weakens, translation decreases current period results relative to the prior period. We had total goodwill of $45.3 million for the Unum International segment at December 31, 2020, of which, $40.2 million is attributed to the Unum UK reporting unit and $5.1 million is attributed to the Unum Poland reporting unit. Fair value of our reporting units is estimated using a combination of the income and market approaches and the key assumptions used are projected earnings and discount rate. To the extent that the future profitability of these reporting units deteriorates from current assumptions, the goodwill related to the reporting units could be at risk for impairment. Shown below are financial results and key performance indicators for the Unum UK product lines in functional currency. Goodwill Unum UK Operating Results Year Ended December 31 2020 % Change 2019 % Change 2018 Adjusted Operating Revenue Premium Income Group Long-term Disability £ 284.2  2.7  % £ 276.8  2.9  % £ 269.0  Group Life 84.6  (6.7) 90.7  9.3  83.0  Supplemental 77.7  11.0  70.0  14.2  61.3  Total Premium Income 446.5  2.1  437.5  5.9  413.3  Net Investment Income 76.0  (16.0) 90.5  4.6  86.5  Other Income 0.1  (50.0) 0.2  N.M. —  Total 522.6  (1.1) 528.2  5.7  499.8  Benefits and Expenses Benefits and Change in Reserves for Future Benefits 352.5  5.1  335.5  9.1  307.4  Commissions 28.1  (1.7) 28.6  5.5  27.1  Deferral of Acquisition Costs (4.2) (22.2) (5.4) 8.0  (5.0) Amortization of Deferred Acquisition Costs 5.3  (1.9) 5.4  (11.5) 6.1  Other Expenses 86.5  3.3  83.7  4.4  80.2  Total 468.2  4.6  447.8  7.7  415.8  Adjusted Operating Income £ 54.4  (32.3) £ 80.4  (4.3) £ 84.0  Weighted Average Pound/Dollar Exchange Rate 1.287  1.279  1.336  Operating Ratios (% of Premium Income): Benefit Ratio 78.9  % 76.7  % 74.4  % Other Expense Ratio 19.4  % 19.1  % 19.4  % Adjusted Operating Income Ratio 12.2  % 18.4  % 20.3  % Persistency: Group Long-term Disability 88.2  % 89.9  % 87.8  % Group Life 81.8  % 89.0  % 88.5  % Supplemental 90.7  % 89.9  % 93.1  % N.M. = not a meaningful percentage 73 (in millions of pounds, except ratios)