For the six months ended June 30, 2021, net income was $4.57 billion, or $10.13 per share, compared with a net loss of $(79) million, or $(0.17) per share, for 2020. Core operating income was $2.76 billion, or $6.13 per share, compared with $966 million, or $2.13 per share, for 2020. The P&C combined ratio was 88.6% compared to 101.0% prior year, and the current accident year P&C combined ratio excluding catastrophe losses was 85.3% compared to 87.5% prior year. Book value was favorably impacted by after-tax net realized and unrealized gains of $785 million, including $264 million in the company's investment portfolio, $297 million from favorable foreign exchange and $203 million from mark-to-market gains in the company's variable annuity reinsurance portfolio.
For the six months ended June 30, 2021 and 2020, the tax expenses (benefits) related to the table above were $(8) million and $(10) million, respectively, for amortization of fair value adjustment of acquired invested assets and long-term debt; $149 million and $(28) million, respectively, for adjusted net realized gains and losses; and $514 million and $191 million, respectively, for core operating income.
Evan G. Greenberg, Chairman and Chief Executive Officer of Chubb Limited, commented: "Chubb had simply an outstanding quarter, highlighted by record core operating earnings and underwriting results. We produced the best P&C premium revenue growth globally in over 15 years, powered by our commercial P&C businesses and supported by continued robust commercial P&C pricing. Operating earnings in the quarter were $1.62 billion or $3.62 per share.
"Our published and current accident year combined ratios of 85.5% and 85.4%, respectively, reflect 200 basis points of underwriting margin improvement, almost entirely loss ratio-related. Current accident year underwriting income of $1.2 billion was up 27%, while on the other side of the balance sheet adjusted net investment income in the quarter of $945 million was also a record and up nearly 9.5% from prior year.
"P&C net premiums written were up 15.5% globally, with commercial premiums excluding agriculture up nearly 21%. For perspective, we have averaged double-digit commercial P&C growth over the past 10 quarters, and both second quarter and year-to-date growth were the strongest since 2004. In North America, we grew our commercial P&C premiums over 16%, while in our international operations premiums grew 33% on a published basis, or 24% in constant dollars. Growth in the quarter was broad based. Net premiums written in our consumer lines remain impacted by the pandemic's effects on travel and other business and consumer-related activity but are beginning to improve and, in fact, increased 5.6% in the quarter.
"We are capitalizing on a strong commercial P&C pricing environment in most all important regions of the world. Overall rates increased in our North America and international commercial P&C businesses by 13.5% and 16%, respectively, and were well in excess of loss costs. From everything we see today, I am confident these market conditions will continue.
"Our company is firing on all cylinders – we are growing our business while we continue to expand underwriting margins. We will continue to outperform and deliver strong, sustainable shareholder value."