The reconciliation of such measures to the most comparable GAAP figures is included in our earnings release, our financial supplement and earnings presentation, all of which are available on our website at aig.com. Finally, today's remarks related to net premiums written growth are presented on a constant dollar basis. Please refer to page 26 of the earnings presentation for reconciliations of such metrics. On the call today, I will review our second quarter financial highlights, provide perspective on the current market environment, and discuss our strategic priorities that will guide our continued progress and growth.
Our performance reflects the benefits of our diversified portfolio, continued momentum from organic growth in our strategic transactions, and disciplined execution by our talented team. Adjusted after-tax income per diluted share was $2, a 10% increase year-over-year, and adjusted after-tax income was $1.1 billion. The accident year combined ratio, as adjusted, was 88.1%, an improvement of 30 basis points from the prior year quarter. The calendar year combined ratio was 89%, also an improvement of 30 basis points over the prior year quarter.
Net premiums written increased 9%, or 11% excluding North American property, reflecting organic growth in select high-performing segments of our global commercial portfolio. Growth in global personal, driven by our Accident & Health and high net worth businesses, and contributions from our recent strategic transactions, which are providing meaningful growth in line with our expectations. International Commercial net premiums written increased 10%, driven by growth in property and marine, partially offset by financial lines, where we continue to be targeted and disciplined in our underwriting. In global commercial, retention was 88%, and new business, including our strategic transactions, was $1.9 billion, a year-over-year increase of 37%.