ZURICH—Swiss voters on Sunday overwhelmingly rejected a controversial initiative that would have guaranteed all Swiss residents a minimum income on which to live.

The Basic Income Initiative received just 23.1% of the vote in Sunday’s referendum, compared with 76.9% against. The outcome was never in doubt, with the government, businesses and many trade unions lining up in opposition and recent polls suggesting the public was firmly against the idea.

Rather, the significance of Sunday’s vote—which the plan’s backers ensured by collecting the necessary 100,000 signatures—was that it gave a high-profile airing to an idea that has gained traction among economists in Europe and the U.S. in recent years.

Though the monthly amount wasn’t spelled out, it was expected to have been around 2,500 Swiss francs ($2,560) per adult, with a smaller subsidy for children, without regard to employment, education, disability, age or even wealth.

Supporters said the policy would provide security at a time of rapid technological change. Backers also said it would simplify the patchwork of agencies charged with overseeing pensions, welfare, disability and other support, saving the government money while freeing people from the bureaucracies of means-tested programs.