Steven A. Zabel
Executive Vice President & Chief Financial Officer at Unum Group
Great. Thanks, Rick, and good morning, everyone.
As Rick described, the first quarter was a very strong start to the year. Before getting into the details, I would like to highlight a few of the key trends that are driving the impressive results across our businesses. First, from the topline perspective, we're seeing high levels of growth in our core operations with premium growth of 6.6%, bolstered by record levels of persistency in our Group lines and nearly 17% premium growth for Unum International.
In addition to growth, our margins continue to be robust with Group Disability maintaining the exceptional benefit ratio levels produced in 2023. Group Life and AD&D earnings at levels not seen since pre-pandemic and long-term care benefits continuing to normalize as expected. Putting it all together, these trends allow us to grow the company's earnings power and further our financial flexibility.
In the quarter, we grew adjusted operating earnings 9.6% to $514.5 million, leading to after tax adjusted operating earnings per share of $2.12, representing growth of 13.4%. On the statutory side, after tax operating income was up 26.9% to $350.5 million, driving further capital strength with RBC and holding company liquidity well in excess of our targets. While we are only one quarter into the year, all of these factors reinforce our confidence in executing against our targets for 2024.
Considering that backdrop, I'll now move to this segment financial results. Starting with Unum US, adjusted operating income increased 23.3% to $385.2 million in the first quarter of 2024, compared to $312.5 million in the first quarter of 2023. Results for all product lines improved year-over-year with our Group Life and AD&D lines seeing the greatest improvement driven by favorable mortality trends leading to a 68.2% benefit ratio.
Natural growth of lives and wages returned to more normal levels of approximately 2% and along with total group persistency of 92.1%, supported premium growth of 6.1% in Unum US. Overall, Unum US sales were lower in the first quarter of 2024 by $2.5 million, or approximately 1% year-over-year.
Group sales increased 2.5% compared to the first quarter of 2023, while sales in supplemental and voluntary lines did not meet our expectations and were down 4%. As Rick mentioned, Group sales performed better than expectations in the quarter and are expected to meet our expectations for the year.
The Group Disability line reported another robust quarter with adjusted operating income of $164.8 million compared to $145.7 million in the first quarter of 2023, with the increase driven by favorable paid [Phonetic] incidence. Along with consistently strong performance and recoveries, the Group Disability benefit ratio was 57.5% in the first quarter compared to 60% in the first quarter of 2023.
Results for Unum US Group Life and AD&D also improved compared to the year ago period, with adjusted operating income of $78.8 million for the first quarter of 2024 compared to $40.1 million in the same period a year ago. As mentioned, the benefit ratio decreased to 68.2% compared to 75% in the first quarter of 2023, driven by lower incidence. The favorability experienced in the quarter does not change our expectations of low to mid 70% benefit ratios in the coming few quarters.
Adjusted operating earnings for the Unum US supplemental and voluntary lines in the first quarter of 2024 increased to $141.6 million from $126.7 million, an increase of 11.8%. The increase is driven by improved underlying benefits experience year-over-year across all lines.
Then moving to Unum International, adjusted operating income in the first quarter decreased to $37.4 million from $38.4 million in the first quarter of 2023 due to a lower benefit -- due to lower benefit from inflation.
Adjusted operating income for the Unum UK business decreased in the first quarter to GBP28.2 million compared to GBP31 million in the first quarter of 2023. Unum UK earnings grew over 10% after removing the direct inflationary benefits, which were still positive in the first quarter of 2024 but significantly lower year-over-year. Unum UK's underlying earnings strength has continued to grow and we now expect the business to earn in the mid to upper GBP20 million pound range per quarter, as inflation subsides.
Premium income for our Unum International business segment increased by 16.8% year-over-year, including 15% growth in Unum UK. Similar to other segments, strong persistency in excess of 90% in both Unum UK and Poland helped to offset decreased sales in the quarter.
Next, adjusted operating income for the Colonial Life segment increased to $113.7 million in the first quarter compared to $93.9 million in the first quarter of 2023. Premium income of $446.9 million grew at a healthy rate of 4.1% compared to a full year 2023 growth rate of 1.4%. Premium growth was driven by higher prior period sales and persistency of 78.4%, or 110 basis points greater than the year ago period. Sales in the first quarter of $103 million decreased 3.6% from prior year.
In the Closed Block segment, adjusted operating income of $24.3 million was higher than last quarter's results of $21.3 million with relatively consistent LTC claims experience earnings were below our expectations due to alternative assets yielding 6.3% in the first quarter on an annualized basis compared to our long-term expectations of 8% to 10%.
Since inception, our diversified alternative portfolio has achieved returns that match our long-term projections, but can be volatile period to period. As we discussed in January, we expect LTC incidence to remain elevated in 2024 as the claim inventory normalizes. While LTC incidence experienced in the first quarter was elevated compared to our long-term expectations, we believe the recent trend continues to indicate a pattern of returning to normal inventory levels.
The LTC net premium ratio is 93.8% in the first quarter of 2024, higher than the 85.3% result in the same year ago period due primarily to the assumption update in the third quarter of 2023. Sequentially, the NPR increased 30 basis points compared to the fourth quarter of 2023 due primarily to the impact of a large case termination in the first quarter.
Finally, we continue to execute on our Closed Block strategy, focusing on creating value, reducing the footprint and increasing predictability of outcomes. As we discussed in January, this includes seeking actuarially justified rate increases. Since the program refreshed in the third quarter of 2023, we have achieved approximately 20% of our target, including approximately 5% in the first quarter of 2024.
So then, wrapping up my commentary on the segment's financial results, the adjusted operating loss in the Corporate segment was $46.1 million compared to a $33.5 million loss in the first quarter of 2023, primarily driven by lower allocated net investment income and higher retirement plan expenses. Our expectation for the remainder of the year is that losses in the Corporate segment will stay relatively consistent in the mid $40 million range.
And then lastly, the effective tax rate of 20.3% in the first quarter was favorable to our expectation of 21.5% to 22%, driven by one-time amended filings of prior year returns.
Moving now to investments, we continue to see a good environment for new money yields and risk management. Purchases made in the quarter were again at levels above our earned portfolio yield, which was 4.35% in the first quarter. Total net investment income was $513.5 million in the first quarter, compared to $508.8 million in the prior year, driven primarily by higher asset levels and higher miscellaneous investment income. Miscellaneous investment income increased in the first quarter to $20.8 million, compared to $15.8 million a year ago, with income from our alternative assets totaling $20.3 million.
In addition, we continued to manage our interest rate risk by expanding our hedge and repositioning programs. Since inception of the program last year, we've entered into $2.7 billion of treasury forwards and repositioned $765 million of assets, including $165 million and $65 million, respectively, in the first quarter of 2024.
I'll end my commentary this morning with an update on our capital position. As laid out at our outlook call, we project this year to be an inflection point in the free cash flow generation profile of the company. Our outlook for strong statutory earnings with no contributions to LTC is expected to drive significant capital strength and financial flexibility in 2024.
Through the first quarter, we're off to a great start with the strong margins discussed in our GAAP results, leading to statutory after tax operating income of $350.5 million in the quarter and repositioning -- and positioning us well for our $1.2 billion to $1.4 billion expectation for the year. With these strong statutory earnings, the weighted average risk based capital ratio for our traditional US insurance companies strengthened further to approximately 440% and holding company liquidity remained robust at $1.4 billion.
While both of these metrics are expected to fluctuate throughout the year, we do expect year end RBC of 415% to 430% and holding company liquidity of greater than $2 billion, both well in excess of our long-term targets, providing us with capital optionality. This optionality already considers our plans to increase shareholder capital return by doubling our share repurchase run rate over 2023 levels to $500 million and increasing our shareholder dividend by 15%, effective in the third quarter.
So then, looking ahead, as we progress throughout the year, we will continue to evaluate the best use of our excess capital in line with our priorities. Overall, we are very pleased with our first quarter results. The strong start to the year sets us up well to execute on our strategy and deliver against our financial targets.
Now, I'll turn the call back to Rick for his closing comments, and I look forward to your questions.