Final answer:
During the late 1990s, several companies, such as Hoffman-La Roche, BASF, and Rhone-Poulenc, were involved in an international cartel that manipulated vitamin prices.
Step-by-step explanation:
During the late 1990s, antitrust regulators prosecuted an international cartel of vitamin manufacturers, including companies such as Hoffman-La Roche, BASF, and Rhone-Poulenc.
These companies had reached agreements on production, pricing, and customer allocation. High-priced vitamins were bought by firms like General Mills, Kellogg, Purina Mills, and Proctor and Gamble, which further increased prices. Hoffman-La Roche pleaded guilty and faced fines and jail time for their involvement.