1. Prison sentences were more commonly imposed when violence or labour union activity was involved. See P Hadlick, Criminal Prosecutions under the Sherman Anti-trust Act (Washington, DC, Randell Inc, 1939), 63–117 (discussing labour and business racketeering cases). During World War I, eight individuals were sentenced to one-year prison terms under the Sherman Act for conspiracies to interfere with munitions shipments. See The Federal Antitrust Laws with Summaries of Cases Instituted by the United States 1890–1951 (Chicago, IL, Commerce Clearing House, 1952), 109–10.
2. In 1921 individuals first reported to prison for having engaged in cartel activity. The case was United States v Alexander & Reid Co, 280 Fed 924, 927 (SDNY 1922) (describing bid rigging by the building contractors). The sentencing of four individuals to a total 10 months was reported by New York Times, 24 November 1921, 4. Some sources incorrectly report that prison sentences for cartel activity were not served until 1959, in the case of United States v McDonough Co, 1960 Trade Cases (CCH) ¶ 69,695 (SD Ohio, 9 December 1959) (order upholding sentences). Four individuals were each sentenced to 90 days for fixing the prices of hand tools such as shovels and rakes, but one died before reporting to prison.