A major component of our Underwriting profit (loss) is due to Net losses and LAE. The following table presents the impact of changes in reserves and reinsurance reinstatement premiums (“RRPs”) on our Net losses and LAE ratio for the years ended December 31, 2015, 2014 and 2013 (note: accident year is abbreviated “AY”):
For the year ended December 31, 2014, we recorded $55.8 million of net prior AY reserve releases primarily driven by $38.3 million, $15.4 million and $2.1 million of reserve releases from our Int’l Insurance, U.S. Insurance and GlobalRe reporting segments, respectively, mostly due to favorable loss emergence. The favorable prior AY reserve releases were partially offset by $16.8 million of current AY losses related to large loss activity. The loss ratio was also unfavorably impacted by $4.4 million of RRPs.
Our Company had three credit related OTTI losses totaling $1.7 million from our equity portfolio during the year ended December 31, 2015, which were for certain common stocks in the energy sector and aerospace industry that were impacted by global economic events. Our Company did not have any credit related OTTI losses for the year ended December 31, 2014. OTTI losses for the year ended December 31, 2013 consisted of $1.8 million for one municipal bond and $0.6 million for three equity securities for which fair value was less than 80% of amortized cost for at least six months.
For the year ended December 31, 2014, our U.S. Insurance reporting segment recorded $15.4 million of net prior AY reserve releases primarily driven by $29.0 million and $3.5 million of reserve releases from our U.S. Marine and U.S. Professional Liability operating segments, respectively. U.S. Marine was favorably impacted by a decline in large loss activity and U.S. Professional Liability benefited from $4.5 million favorable loss emergence within D&O due to a cash settlement of a contract dispute with a former third party administrator, partially offset by unfavorable loss emergence from our E&O division. The aforementioned releases were partially offset by $17.1 million of prior AY reserve strengthening in our U.S. P&C operating segment, primarily related to unfavorable loss activity in our Primary Casualty division. The loss ratio was also unfavorably impacted by $1.8 million of RRPs, primarily within our U.S. Marine operating segment.
For the year ended December 31, 2013, our Int’l Insurance reporting segment recorded $27.3 million of net prior AY reserve releases, driven by our Int’l Marine operating segment of $6.4 million and our Int’l P&C operating segment of $22.3 million due to favorable loss emergence from prior years. These releases were partially offset by $1.3 million of net prior AY strengthening in our Professional Liability operating segment.
Gross written premiums increased $7.3 million for the year ended December 31, 2014 compared to the same period in 2013, primarily driven by new property treaty business and additional LatAm business in our P&C product and an increase in RRPs in our Marine and P&C products. Gross written premiums growth was partially offset by a reduction in renewal premiums from our A&H and Agriculture products.
As of December 31, 2015, we own $58.4 million of municipal securities, which are credit enhanced by various financial guarantors which have an average underlying credit rating of AA-. There has been no material adverse impact to our investment portfolio or results of operations as a result of downgrades of the credit ratings for several of the financial guarantors.
Details of the collateral of our asset-backed securities portfolio as of December 31, 2015 are presented below:
Hurricane Joaquin impacted the fourth quarter of 2015 with a total estimated net loss of $10.0 million and $4.0 million in additional RRPs.
The following table provides a sensitivity analysis of our Net loss reserve as of December 31, 2015: