While the cassette resurgence has not matched the vinyl boom, tape sales are on the rise, growing 23% in 2018. This has led to a period of immense productivity for National Audio Company, the largest audio cassette tape manufacturer in the United States. Production is being threatened, however, by a worldwide shortage of gamma ferric oxide, the most common material used for magnetic recording.

According to a letter from NAC to its customers, verified by Pitchfork, the only factory that refines gamma ferric oxide has been “under renovation” for much of the year, resulting in smaller amounts of the material being shipped to NAC and subsequently a backlog in cassette production. The factory hopes to resume normal production by the end of the year.