Our ability to write new business depends, among other things, on a steady flow of high-L TV mortgages that require our  mortgage insurance. Losses from the housing market downturn have caused lenders to substantially reduce the availability of  these loans and to significantly tighten their underwriting standards. Fewer loan products and tighter loan qualifications, while  improving the overall quality of new mortgage originations, have in turn reduced the number of qualified homebuyers and  made it more difficult for buyers (in particular first-time buyers) to obtain mortgage financing or to refinance their existing  mortgages. In addition, the significant disruption in the housing and related credit markets that began in 2007 led to reduced  investor demand for mortgage loans and MBS in the secondary market, which historically has been a source of funding for  many mortgage lenders. This significantly reduced liquidity in the mortgage funding marketplace, forcing many lenders to  retain a larger portion of their mortgage loans and MBS and leaving them with less capacity to continue to originate new  mortgages. Total domestic mortgage originations have decreased significantly from the $2.7 trillion in 2006 (pre-dating the housing  downturn) to approximately $1.9 trillion for 2012. If the volume of new mortgage originations continues to remain at low levels  for a prolonged period, we will likely experience fewer opportunities to write new insurance business and we may be subject to  increased competition with respect to these opportunities, which could reduce the size of our mortgage insurance business and  have a significant negative ef fect on both our ability to execute our business plans and our overall franchise value. See “ Our  mortgage insurance business faces intense competition .” Further, the Dodd-Frank Act’s reforms to strengthen lending  standards, improve underwriting standards and increase accountability in the loan origination and securitization processes could  further reduce the total number of mortgage originations in the future, in particular with respect to the high-L TV market. In  addition, the proposed Basel III guidelines, unlike previous Basel rules, do not recognize private mortgage insurance as a factor  that reduces risk when calculating a loan’ s risk weighting, which could discourage the use of mortgage insurance and result in  fewer opportunities for us to write new business. See “ Legislation and regulatory changes and interpretations could harm our  mortgage insurance business ” and “ The implementation of the Basel II capital adequacy requirements and the Basel III  guidelines may discourage the use of mortgage insurance .”  A decrease in the volume of home mortgage originations could result in fewer opportunities for us to write new insurance  business.  Our NIW and franchise value could decline if we lose a significant customer. Our mortgage insurance business depends on our relationships with our customers, and in particular , our relationships  with our largest lending customers. As of December 31, 2012, our top 10 mortgage insurance customers (measured by NIW)  were generally responsible for 24.8% of our primary NIW  in 2012. Since 2011, we have been focused on expanding and  diversifying our customer base, and in 2012, 20.8% of our NIW  was from customers new to us in 2011 and 2012.  Notwithstanding this diversification trend, maintaining our business relationships and business volumes with our lar gest lending  customers remains critical to the success of our business. In response to the most recent deterioration in housing markets, we have tightened our underwriting guidelines, which has  resulted in our declining to insure some of the loans originated by our lar ger customers. We have also increased our pricing to  reflect the increased risk of default in the current economic and housing downturns. Our increased pricing, tighter guidelines  and increased level of loss mitigation activity has negatively af fected our relationships with certain of our customers and could  result in customers choosing to limit the amount of business they conduct with us or cease to do business with us entirely . See  “ Insurance rescissions and claim denials are not expected to continue at the elevated levels we have been experiencing and a  number of our lender customers are challenging our loss mitigation actions .”  Our master insurance policies and related lender agreements do not, and by law cannot, require our mortgage insurance  customers to do business with us. Although we have taken steps to significantly expand and diversify our customer base in  recent years, we cannot be certain that any loss of business from a single lender would be replaced from other new or existing  lending customers in the industry. As a result of current market conditions, our lending customers may decide to write business  only with certain mortgage insurers based on their views with respect to an insurer ’s pricing, underwriting guidelines, loss  mitigation practices, financial strength or other factors. In addition, many of our customers currently are placing a significant  portion of their mortgage insurance business with us. Our customers may choose to diversify the mortgage insurers with which  they do business, which could negatively af fect our level of NIW and our market share.  70