The Pension Benefit Guaranty Corporation's (PBGC) Pension Insurance Modeling System (PIMS) is used to evaluate the financial security and resilience of the national program backstopping private defined benefit plans. The Pension Research Council of the Wharton School at the University of Pennsylvania recently convened a Technical Review Panel of experts to review key inputs, outputs, and model assumptions. Our review was intended to provide a formal evaluation of the technical adequacy of the model by outside experts. The papers herein summarize views of each expert on this project. Key findings are as follows:

• • The PIMS models are an important and valuable tool in modeling the Pension Benefit Guaranty Corporation's liability risk. To the best of our knowledge, there is no other model that can do a comparable job.

• • Nevertheless, some improvements could be integrated in the Agency's approach to modeling. Those deserving highest priority attention, in the experts’ view, include incorporating systematic mortality risk (i.e., treat mortality and longevity as stochastic variables); including new asset classes increasingly found in defined benefit plan portfolios (e.g., commercial real estate, private equity funds, infrastructure, hedge funds, and others); developing a more complex model for the term structure of interest rates; and incorporating an option value approach to pricing the insurance provided.

• • The Agency could also do more to communicate the range of uncertainty and potential for problems associated with the PBGC's financial status. This could include additional information including the conditional value-at-risk, and perhaps an ‘intermediate,’ ‘optimistic’, and ‘pessimistic’ set of projected outcomes, as well as the expected ‘date of exhaustion’ for assets backing pension benefits insured by the PBGC.

The financial market assumptions of the Pension Benefit Guaranty Corporation (PBGC)'s Pension Insurance Modeling System model are critical inputs to simulations for most apparent uses of the system. They currently appear to be based on a reduced form, ‘classical’ approach to assessing and forecasting the distribution of returns on various classes of input assets, allowing for a fairly sophisticated and useful approach to understanding simulated distributions of potential pension insurance outcomes as well as the net financial status of the PBGC. This technical note discusses some of the capital market side assumptions utilized in the model. It also comments on important related assumptions including the assumed asset allocations of insured plans, making suggestion for possible modification of input assumptions of the model to reflect time variation in financial market return behavior as well as time variation in observed plan allocations.

Financial economics holds that payment streams should be valued using discount rates that reflect the cash flows’ risks. In the case of pension liabilities, the appropriate discount rate for a pension fund's liabilities is the expected rate of return on a portfolio that would be held under a liability-driven investment policy. The valuation of defined benefit pension obligations involves choices revolving around deciding: (1) what future benefit payments to recognize today (i.e., which liability concept to use); and (2) from whose point of view to value the liabilities. Moving towards modeling, the distribution of future liabilities using a ‘risk-neutral’ framework, would allow for calculating the present value of the future liabilities more accurately. This would provide policymakers with information more relevant for the decision-making, and it would also permit easier communication of the risks facing the Pension Benefit Guaranty Corporation's PIMS model via a single univariate statistic.

The Pension Benefit Guaranty Corporation (PBGC) insures private sector defined benefit (DB) pension plans, when an employer becomes insolvent and is unable to pay the pension liabilities. In principle, the insurance premiums collected by PBGC should be sufficient to cover potential losses; this would ensure that PBGC could pay the insured benefits of terminated pension plan without additional external funding (e.g., from taxpayers). Therefore, the risk exposure of the PBGC from insuring DB pension plans arises from the probability of the employer insolvencies; and the terminating plans’ funding status (the excess of the value of the insured plan liabilities over the plan assets). Here we explore only the second component, namely the impact of plan underfunding for the operation of the PBGC. When a DB plan is fully funded, the PBGC's risk exposure for an ongoing plan is low even if the plan sponsor becomes insolvent. Thus the questions most pertinent to the PBGC are: what key risk factors can produce underfunding in a DB plan, and how can these risk factors be quantified? We discuss the key risk factors that produce DB pension underfunding, namely, investment risk and liability risk. These are interrelated and must be considered simultaneously in order to quantify the risk exposure of a DB pension plan. We propose that an integrated risk management model (an Integrated Asset/Liability Model) can help better understand DB pension plan funding risk. We also examine the Pension Insurance Modeling System developed by the PBGC in terms of its own use of some of the building blocks of an integrated risk management model.

We discuss pension system risk in the USA, focusing on the investment policy and the methodology for the valuation of the liabilities of the Pension Benefit Guaranty Corporation (PBGC). We offer suggestions as to how the PBGC should consider modifying the Pension Insurance Modeling System. The issues of investment policy and liability valuation are not two distinct topics. As emphasized here, the proper valuation of liabilities provides a benchmark for the PBGC to use as a starting point for the establishment of its investment policy and then for assessing investment performance.

When a private pension plan sponsor with an underfunded plan becomes insolvent, the difference between the value of the plan's assets and its termination liabilities represents a liability for the Pension Benefit Guaranty Corporation (PBGC). Hence, accurately modeling the joint statistical distribution over time of defined benefit pension underfunding and sponsor terminations is critical for estimating PBGC's prospective cash flows and evaluating its financial position. It appears that the current Pension Insurance Modeling System (PIMS) approach to modeling risk does a reasonable job of capturing its statistical properties effects on PBGC cash flows, although some of the aspects might be improved, and metrics expanded. The present paper outlines, how an option-based approach to modeling the joint distribution of defaults and underfunding in PIMS might be implemented, while preserving the strengths of the current model. Moving to an option-based approach would allow PIMS to be used to estimate the fair values of future liabilities. Such an approach could have a significant effect on the perceived financial position of PBGC.

The Pension Benefit Guaranty Corporation's (PBGC) Pension Insurance Modeling System model has taken on the Herculean task of modeling in detail and under many scenarios the cash outflows associated with the pension obligations, they have assumed. This paper's comments are focused almost entirely upon the PBGC's termination liabilities, and address four pressing issues: (1) the need to discount the liability stream by current riskless interest rates instead of using corporate bond rates that reflect credit risk, call risk, and other risks, or using some ad hoc prescribed average of past rates; (2) the need to use a term structure of interest rates; (3) the need to employ more useful investment management benchmarks; and (4) how to implement a relevant and rigorous liability benchmark.