Our insurance segment reported an underwriting loss of $46 million for the quarter, compared to underwriting income of $22 million for the fourth quarter of 2011. The current quarter’s underwriting results reflected a combined ratio of 112.2%, compared with 94.1% in the prior year quarter. The segment’s current accident year loss ratio increased from 68.9% in the fourth quarter of 2011 to 88.9% this quarter, driven by a higher level of natural catastrophe losses. The current quarter's result includes aggregate pre-tax net losses (inclusive of premiums to reinstate reinsurance protection) of $178 million, or 44.9 points, for Storm Sandy; in addition, we recognized an aggregate $13 million, or 3.4 point, reduction in our estimate for events of the first nine months (including Hurricane Isaac and U.S. weather events in the first half of the year). Comparatively, the fourth quarter 2011 result included $28 million, or 7.6 points, of catastrophe and weather-related losses (inclusive of premiums to reinstate reinsurance protection), primarily related to the Thai Floods. Exclusive of these amounts, the fourth quarter current accident year loss ratio decreased in 2012, driven by a number of factors. Most notable was a reduction in property and energy losses, the frequency of which was high in the fourth quarter of 2011.
Net favorable prior year reserve development was $40 million, or 10.5 points, this quarter compared with $29 million, or 7.8 points, in the fourth quarter of 2011.
The reduction in the segment's acquisition cost ratio for the quarter was driven by the aforementioned changes in reinsurance programs at the second quarter renewal, as well as commissions associated with the reinstatement of our reinsurance protection. The increase in fourth quarter general and administrative expenses was the result of higher performance-related compensation costs.
For the full year, underwriting income was $65 million compared with $35 million in 2011. Growth in net premiums earned, an improved current accident year attritional loss ratio and an increase in favorable prior year reserve development more than offset a higher level of natural catastrophe-related losses.