The Economics Cassette Series was a bi-weekly, subscription-based series that ran from 1968 to 1978. Instructional Dynamics Incorporated (IDI) produced the series, which served as something of a companion to Friedman's Newsweek columns of the same era. There are 215 total cassettes in the series. As a general rule, every cassette features the same program on both sides. Each program is an interview with Milton Friedman, recorded either in Chicago, Illinois or in Vermont, in which he commented on current economic events. The Chicago programs were recorded at the Friedman residence with William Clark of the Chicago Tribune conducting the interviews. Dr. Friedman's wife, Rose, conducted the interviews in the Vermont recordings. An exception to the above is a guest appearance by Paul A. Samuelson. The series ended after IDI ran into financial difficulties.