On Nov 10, 1981 the IRS issued the first regulations for the 401K salary deferrals. Deferred tax plans (CODAs) had been around since
1956, but in more limited forms and for high income employees. They were seen a supplemental retirement savings to pensions until the the 1990s when they became often the sole corporate retirement plan. And until the mid-80s administrations periodically proposed eliminating CODAs and 401Ks to increase tax revenues.