Wharton Pension Research Council Working Papers

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Working Paper

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The financial market assumptions of the PBGC’s PIMS 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.


The author thanks Jeff Brown and staff members of the DOL, PBGC and SSA for helpful comments and Kyle Binder, Alimu Abudu, and Ankur Dadhania for helpful research assistance.

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Copyright/Permission Statement

All findings and conclusions expressed are solely those of the author and do not represent the views of the SSA or any agency of the federal government, the MRRC, the PRC, or The Wharton School at the University of Pennsylvania. Comments welcome.


The research reported herein was pursuant to a grant from the U.S. Social Security Administration (SSA) funded as part of the Retirement Research Consortium (RRC); the author also acknowledges support from The Pension Research Council at The Wharton School.

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Date Posted: 26 June 2019