*nderHriting Resu=ts 3J Seg>ent Property Segment Below is a summary of the underwriting results and ratios for our Property segment: .ear ended De4e>3er       (in thousands, except percentages) Gross premiums written $ 3,958,724 $ 2,999,142 $ 2,430,985 Net premiums written $ 2,868,002 $ 2,037,200 $ 1,654,259 Net premiums earned $ 2,608,298 $ 1,936,215 $ 1,627,494 Net claims and claim expenses incurred 2,163,016 1,435,947 965,384 Acquisition expenses 487,178 353,700 313,554 Operational expenses 143,608 135,547 138,187 Underwriting income (loss) $ (185,504) $ 11,021 $ 210,369 Net claims and claim expenses incurred – current accident year $ 2,396,389 $ 1,592,996 $ 968,357 Net claims and claim expenses incurred – prior accident years (233,373) (157,049) (2,973) Net claims and claim expenses incurred – total $ 2,163,016 $ 1,435,947 $ 965,384 Net claims and claim expense ratio – current accident year 91.9 % 82.3 % 59.5 % Net claims and claim expense ratio – prior accident years (9.0) % (8.1) % (0.2) % Net claims and claim expense ratio – calendar year 82.9 % 74.2 % 59.3 % Underwriting expense ratio 24.2 % 25.2 % 27.8 % Combined ratio 107.1 % 99.4 % 87.1 % Property Gross Premiums Written In 2021, our Property segment gross premiums written increased by $959.6 million, or 32.0%, to $4.0 billion, compared to $3.0 billion in 2020. Gross premiums written in the catastrophe class of business were $2.2 billion in 2021, an increase of $349.0 million, or 18.5%, compared to 2020. The increase in gross premiums written in the catastrophe class of business included $339.7 million of reinstatement premiums associated with the 2021 Weather- Related Large Losses, compared to reinstatement premiums of $77.0 million associated with the 2020 Weather-Related Large Loss Events and $25.9 million associated with COVID-19 losses in 2020. The growth in 2021 was also driven by an improved rate environment, increased shares on existing deals, participation in new deals and opportunities across underwriting platforms. Gross premiums written in the other property class of business were $1.7 billion in 2021, an increase of $610.6 million, or 54.9%, compared to 2020. The increase in gross premiums written in the other property class of business was primarily driven by rate improvements which contributed to growth in new and existing business written in the current and prior periods across underwriting platforms. This included growth in catastrophe exposed U.S. property excess and surplus lines. In 2020, our Property segment gross premiums written increased by $568.2 million, or 23.4%, to $3.0 billion, compared to $2.4 billion in 2019. Gross premiums written in our catastrophe class of business were $1.9 billion in 2020, an increase of $291.3 million, or 18.3%, compared to 2019. The increase in gross premiums written in our catastrophe class of business in 2020 was primarily driven by expanded participation on existing transactions, certain new transactions, rate improvements and business acquired as a result of the acquisition of TMR. 78