Chubb Ltd

7. Unpaid losses and loss expenses

The following table presents a reconciliation of beginning and ending Unpaid losses and loss expenses:

(2)Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments, earned premiums, and A&H long-duration lines totaling $(18) million and $46 million for the three months ended March 31, 2025 and 2024, respectively.

Net unpaid losses and loss expenses increased $1,120 million for the three months ended March 31, 2025, principally reflecting underlying exposure growth and net catastrophe losses, partially offset by the impact of favorable prior period development and crop activity.

Prior Period Development

Prior period development (PPD) arises from changes to loss estimates recognized in the current year that relate to loss events that occurred in previous calendar years and excludes the effect of losses from the development of earned premium from previous accident years. Long-tail lines include lines such as workers' compensation, general liability, and financial lines; while short-tail lines include lines such as most property lines, energy, personal accident, and agriculture. The following table summarizes (favorable) and adverse PPD by segment:

Significant prior period movements by segment, principally driven by reserve reviews completed during each respective period, are discussed in more detail below. The remaining net development for long-tail lines and short-tail business for each segment and Corporate comprises numerous favorable and adverse movements across a number of lines and accident years, none of which is significant individually or in the aggregate.

North America Commercial P&C Insurance. Net favorable development for the three months ended March 31, 2025, included $163 million from short-tail lines, primarily from surety, due to lower-than-expected loss development. This favorable development was partially offset by net adverse development of $49 million from long-tail lines, primarily from general casualty partially offset by favorable development in workers' compensation and financial lines.

Net favorable development for thethree months ended March 31, 2024, included $144 million from short-tail lines, primarily from surety and property and marine lines due to lower-than-expected loss development. The favorable development was partially offset by net adverse development of $96 million from long-tail lines, primarily in commercial excess and umbrella lines, driven by higher-than-expected loss development.

Overseas General Insurance. Net favorable development for the three months ended March 31, 2025, included a $122 million release from short-tail lines.

Net favorable development for the three months ended March 31, 2024, included $88 million from short-tail lines, primarily from property lines driven by favorable development across all regions, primarily in accident years 2020 through 2023.