Other Municipal Bonds. These bonds include other debt issued, guaranteed or otherwise supported by U.S. national or  local governmental authorities, as well as student loans, revenue bonds and obligations of certain not-for -profit organizations.  Other municipal bonds also include other types of municipal obligations, including human service providers, second-to-pay ,  international public finance, non-profit institutions and infrastructure bonds (which are obligations issued by a variety of  entities engaged in the financing of infrastructure projects, such as roads, airports, ports, social infrastructure and other physical  assets delivering essential services supported by long-term concession arrangements with a public sector entity). Our structured finance business includes financial guaranty insurance of  ABS and other asset-backed or mortgage-backed  obligations, including both funded and synthetic CDOs. Asset-Backed Obligations. Funded asset-backed obligations usually take the form of a secured interest in a pool of assets,  often of uniform credit quality , such as credit card or auto loan receivables, commercial or residential mortgages or life  insurance policies. Funded ABS also may be secured by a few specific assets such as utility mortgage bonds and multi-family  housing bonds. In addition, we have insured future flow DPRs transactions, where our insured obligations are backed by  electronic payment orders intended for third-party beneficiaries (e.g., trade-related payments, individual remittances and foreign  direct investments). The performance of synthetic asset-backed obligations is tied to the performance of specific pools of assets, but the  obligations are not secured by those assets. Most of the synthetic transactions we insure are CDOs.  CDOs. In many of these transactions, primarily our corporate CDOs, we generally are required to make payments to our  counterparty above a specified level of subordination, upon the occurrence of credit events related to the borrowings or  bankruptcy of obligors contained within pools of corporate obligations or , in the case of pools of mortgage or other asset- backed obligations, upon the occurrence of credit events related to the specific obligations in the pool.  When we provide  synthetic credit protection on a specific obligation, our payment obligations to our counterparties are generally the same as  those we have when we insure credits through a financial guaranty insurance policy . However, unlike most of our financial  guaranty insurance policy obligations, where we have subrogation and other rights and remedies, we generally do not have  recourse or other rights and remedies against the issuer and/or any related assets for amounts we may be obligated to pay under  synthetic transactions. Even in those synthetic transactional cases where we have recourse or any rights and remedies, such  recourse, rights and remedies are generally much more limited than the recourse, rights and remedies we generally have in our  more traditional financial guaranty transactions, and frequently need to be exercised indirectly through our counterparty . A CDO pool typically is composed of assets of varied credit quality and dif ferent characteristics with respect to interest  rates, amortization and level of subordination.  We primarily have provided credit protection in our CDO portfolio with respect  to the following types of collateral: corporate debt obligations,  TruPs, commercial mortgage-backed securities (“CMBS”), ABS  (including RMBS), collateralized loan obligations (“CLOs”) and CDOs containing a combination of such collateral types. Corporate CDOs. In our corporate CDO transactions, we provide credit protection for certain specified credit events  related to the borrowings or bankruptcy of obligors contained within pools of corporate obligations.  We only insure notional  amounts for these transactions (and not any interest payments or other amounts).  All of our outstanding corporate CDOs are  static pools, meaning that the covered reference entities generally cannot be changed without our consent.  The same corporate obligor may exist in a number of our corporate CDO transactions. However , the pool of corporate  entities in our directly insured corporate CDO portfolio is well diversified, with no individual exposure to any corporate entity  exceeding 1.1% of our notional exposure to corporate entities in our directly insured corporate CDOs as of  December 31, 2012.  As of December 31, 2012, our five largest exposures to corporate entities represented approximately 4.4% of our total  aggregate notional exposure to corporate entities in our directly insured corporate CDO portfolio. The number of corporate entities in our directly insured corporate CDO transactions range between 77 and 124 per  transaction, with the concentrations of each corporate entity averaging 1.1% per transaction, but not exceeding 2.6% in any  transaction. Our notional exposure to any single corporate entity in any one transaction ranges from $3.3 million to $120.0  million, with an average of $32.7 million per transaction. 28 2.  Structured Finance