[영문]Supplemental Security Income (SSI) program features have changed little since 1974, and elderly participation has declined over time. A behavioral model of aged household SSI participation is used to simulate various policy alternatives. The failure to index asset limits has had little effect on participation, but the indexation of both asset and income disregard limits would have raised the SSI participation rate of aged households by about 30%. If, in addition, states had been required to hold the real value of their supplemental benefits constant over time, the elderly household SSI participation rate would have doubled. Finally, the model is used to estimate the impact of a recent policy change, the increase in the normal retirement age (NRA) in the regular Social Security system. When fully phased in, the increase in the NRA is predicted to raise the SSI participation of elderly households from 4.9% to 7.8%.