gross written premiums. Premiums earned increased by 14.1% to $4,753.5 million in 2013, compared to $4,164.6 million in 2012. Unlike written premiums, premiums earned were minimally impacted by the Florida quota share reinsurance contract. The change in premiums earned was comparable to net written premiums, excluding the impact of the Florida quota share reinsurance contract.
Commission, Brokerage, Taxes and Fees. Commission, brokerage, taxes and fees increased by 2.6% to $977.6 million for the year ended December 31, 2013 compared to $952.7 million for the year ended December 31, 2012. The year over year changes were primarily due to the impact of the increase in premiums earned, partially offset by an increase in excess of loss business in 2013 which carries a lower commission rate than pro rata business.
The U.S. Reinsurance operation writes property and casualty reinsurance and specialty lines of business, including Marine, Aviation, Surety and A&H business, on both a treaty and facultative basis, through reinsurance brokers, as well as directly with ceding companies primarily within the U.S. The International operation writes foreign property and casualty reinsurance through Everest Re’s branches in Canada and Singapore and through offices in Brazil, Miami and New Jersey. The Bermuda operation provides reinsurance and insurance to worldwide property and casualty markets through brokers and directly with ceding companies from its Bermuda office and reinsurance to the United Kingdom and European markets through its UK branch and Ireland Re. The Insurance operation writes property and casualty insurance, including medical stop loss insurance, directly and through general agents, brokers and surplus lines brokers within the U.S. and Canada. The Mt. Logan Re segment represents business written for the segregated accounts of Mt. Logan Re, which were formed on July 1, 2013. The Mt. Logan Re business represents a diversified set of catastrophe exposures, diversified by risk/peril and across different geographical regions globally.
Cash and Invested Assets. Aggregate invested assets, including cash and short-term investments, were $16,596.5 million at December 31, 2013, an increase of $20.3 million compared to $16,576.2 million at December 31, 2012. This increase was primarily the result of $1,098.3 million of cash flows from operations, $258.9 million in fair value re-measurements, $143.0 million of subscription advances for third party investment into Mt. Logan Re, $87.5 million from external third party capital investment into Mt. Logan Re, $51.5 million from common share issuance under share based compensation plans, net of expense incurred, and $45.9 million in equity adjustments of our limited partnership investments, partially offset by $621.9 million paid for share repurchases, $467.2 million of pre-tax unrealized depreciation, $329.9 million paid to redeem junior subordinated debt securities, $106.7 million paid out in dividends to shareholders, $66.5 million of amortization bond premium, $54.2 million due to fluctuations in foreign currencies and $2.8 million of unsettled securities.
Capital. Our business operations are in part dependent on our financial strength and financial strength ratings, and the market’s perception of our financial strength, as measured by shareholders’ equity, which was $6,968.3 million at December 31, 2013 and $6,733.5 million at December 31, 2012. On March 25, 2013, Moody’s downgraded the Company and its subsidiaries, including the senior debt of Everest Reinsurance Holdings, Inc., by one level. While Moody’s believes that our profitability, fixed charge coverage and market position are very good, the rating agency concluded that our business franchise and diversity and predictability of earnings position us more appropriately with peers at the adjusted rating level. A.M. Best and Standard & Poor’s affirmed ratings for the Company and its subsidiaries on July 25, 2013 and May 23, 2013, respectively. We continue to possess significant financial flexibility and access to the debt and equity markets as a result of our perceived financial strength, as evidenced by the financial strength ratings as assigned by independent rating agencies.
From time to time, we have used open market share repurchases to adjust our capital position and enhance long term expected returns to our shareholders. On May 15, 2013, our existing Board authorization to purchase up to 20 million of our shares was amended to authorize the purchase of up to 25 million shares. As of December 31, 2013, we had repurchased 20.4 million shares under this authorization.
Our liquidity requirements are generally met from positive cash flow from operations. Positive cash flow results from reinsurance and insurance premiums being collected prior to disbursements for claims, which disbursements generally take place over an extended period after the collection of premiums, sometimes a period of many years. Collected premiums are generally invested, prior to their use in such disbursements, and investment income provides additional funding for loss payments. Our net cash flows from operating activities were $1,098.3 million, $694.6 million and $717.7 million for the years ended December 31, 2013, 2012 and 2011, respectively. Additionally, these cash flows reflected net tax payments of $69.3 million and $59.8 million and a net tax refund of $44.5 million for the years ended December 31, 2013, 2012 and 2011, respectively and net catastrophe loss payments of $490.7 million, $551.3 million and $559.2 million for the years ended December 31, 2013, 2012 and 2011, respectively.
Management estimates that the projected net economic loss from its largest 100-year event in a given zone represents approximately 11% of its projected 2014 shareholders’ equity. Economic loss is the PML exposure, net of third party reinsurance and the noncontrolling interests of Mt. Logan Re, reduced by estimated reinstatement premiums to renew coverage and estimated income taxes. The impact of income taxes on the PML depends on the distribution of the losses by corporate entity, which is also affected by inter-affiliate reinsurance. Management also monitors and controls its largest PMLs at multiple points along the loss distribution curve, such as loss amounts at the 20, 50, 100, 250, 500 and 1,000 year return periods. This process enables management to identify and control exposure accumulations and to integrate such exposures into enterprise risk, underwriting and capital management decisions.