The reconciliation of such measures to the most comparable GAAP figures is included in our earnings release, financial supplement, and earnings presentation, all of which are available on our website at aig.com. Please refer to page 29 of the earnings presentation for reconciliations of such metrics reported on a comparable basis. We delivered adjusted after-tax income per diluted share of $1.96, a 51% increase year-over-year. Global commercial net premiums written grew 3%, despite North America Retail Property contracting due to our reduced appetite given the current market environment.
We had strong new business growth led by International Commercial, which grew an impressive 14% year-over-year. The calendar year combined ratio was 88.8%, an improvement of 370 basis points from the prior year quarter. Adjusted after-tax income per diluted share was $7.09, an increase of 43% year-over-year. Adjusted after-tax income for the year was $4 billion, an increase of 24% year-over-year.
For the full year 2025, we generated underwriting income of $2.3 billion, an increase of 22% year-over-year. For full year 2025, Global Commercial net premiums written were $17.4 billion, an increase of 3% year-over-year. Adjusting for the large closeout transaction in our Casualty portfolio that benefited overall growth in that prior year, net premiums written increased 4%. North America Commercial grew net premiums written by 4% or 5% when adjusting for the large closeout transaction, with balanced growth across the portfolio that was partially offset by Retail Property, which contracted 8%.