The USC study, released on March 13, analyzed the prices that 1.6 million people paid for 9.5 million prescriptions in the first half of 2013, based on data from Optum Clinformatics, an organization that sells anonymized claims data for analysis, and National Average Retail Price (NARP) data, which contained drug prices paid by insurers and was based on a national survey of pharmacists.

It showed that the overpayments totaled $135 million during that six-month period.