Please note this event is being recorded.
I would now like to turn the conference over to Bart Hedges, Chief Executive Officer. Please go ahead.
Good morning. I am Bart Hedges, Chief Executive Officer of Greenlight Re. Thank you for taking the time to join us today.
We are very pleased to announce that during third quarter, A.M. Best upgraded our Cayman-based operating company to full “A” from "A-." We believe that this upgrade represents a significant step forward for our reinsurance platform and recognizes the strength of our capital positions, the experience of our team, the success of our differentiated business model and our financial performance. In the short term, we believe the effects of the upgrade will be modest. Over the long term, however, we believe the higher ratings will allow us to access certain classes of casualty business and larger transactions. In short, we expect to be able to develop more opportunities from which we can select the best partners and best risk adjusted returns.
In the third quarter of 2011, in what remains a challenging market for reinsurers and investors alike, Greenlight Re generated a small loss in our underwriting portfolio and a small gain in our investment portfolio. Overall, our fully diluted adjusted book value per share decreased by 0.4% in the quarter and by 7.7% for the first nine months of the year. Our year-to-date combined ratio of 103.3% has deteriorated slightly from our combined ratio of 102.1% reported last quarter. This is mainly due to adverse development on a commercial auto program that is in runoff.
Our gross written premium is flat for the year-to-date when compared to the same period in 2010. Overall, an increase in premiums written from frequency business primarily Florida homeowners business has offset a reduction in the severity business we have written in 2011. The Florida homeowners market continues to show its signs of improvement with their partners experiencing double-digit rate increases. In addition, there have been recent positive legislative changes implemented to mitigate frauds associated with sink hole claims.