In contrast, the SOA literature includes discussions of the various credit modeling techniques, factor-based approaches, credit migration models, structural models, reduced form models, hybrid models, actuarial models and credit scoring models. Several articles provide a brief survey of the various models. Other articles provide in-depth discussion of a particular type of model. Ten Lohuis and Narayanan’s (2004) presentation at the 2004 Investment Actuary Symposium provides an excellent introduction describing how two insurers view and apply credit risk modeling. Farr et al. (2008) provide a brief discussion of various modeling methods, including factor-based approaches, applications of structural and stochastic models, the interaction of assets and liabilities, and stress tests for credit spread modeling. Industry practice is often its own area of independent interest and research: Buff (1992), in the context of asset and liability management, presents a way to study default risk using interactive cash-flow projections of assets and liabilities that are computed along a set of scenarios of default rates. Zurcher (1993) discusses the stochastic modeling and "select/ultimate" default rates used to develop the original bond RBC C-1 factors. Shipperlee (2006) provides presentation slides for an introductory review of how insurance companies manage credit risk. The presentation discusses probability of default, loss given default, credit scoring and data issues. Megregian et al. (2010) find that among surveyed companies, a "reduction to yield" is the most popular way to reflect asset default in pricing, although the smallest companies consider asset default as not material. Sharpe (2011) has a presentation covering governance tools for credit risk management, probability of default, loss given default, rating transitions, simulation, valuation at horizon, credit earnings at risk, and appendix to determine correlations.