The abstract of a Working Paper issued by Yonathan Ben-Shalom and Arif A. Mamun of Mathematica Policy Research, a big contractor for Social Security:
We follow a sample of working-age Social Security Disability Insurance (DI) program beneficiaries for five years after their first benefit award to learn how certain factors help or hinder achievement of four return-to-work milestones: (1) enrollment for employment services provided by a state vocational rehabilitation agency or employment network, (2) start of trial work period (TWP), (3) completion of TWP, and (4) suspension or termination of benefits because of work. We find that younger beneficiaries are more likely than older beneficiaries to achieve the milestones and that substantial variation exists across impairment types. In addition, black beneficiaries and beneficiaries with higher levels of education have a greater probability of achieving the milestones, everything else equal. Also, such achievement is more probable if state unemployment is low at the time of the award. The probability of achieving the milestones is reduced by having a higher DI benefit amount at award, an award decision made at a higher adjudicative level, and by receiving Supplemental Security Income or Medicare benefits at the time of DI award. Finally, we find large variation in the relationships between state of residence and return-to-work outcomes and between award month and return-to-work outcomes. We attribute these variations to unobserved factors at the state level, policy changes over time, and trends in unobserved beneficiary characteristics.