National linked, longitudinal datasets allow us to follow Medicare beneficiaries across the care continuum (all settings) over time and are extremely valuable for evaluation.

When deciding which interventions to study, we frequently use these data to retrospectively identify similar provider sites (a comparison group) and examine changes in outcomes over time. A comparison group helps us determine whether or not improvement is attributable to the intervention or other factors.

When designing and conducting studies, these data give us a rich and nuanced understanding of care delivery and outcomes. They also allow us to conduct evaluations efficiently and often at low cost, paying minimal data reuse fees.