This is the first time that the unions have succeeded in having a proposal adopted by direct democracy.
The vote is considered historic. The Swiss have spoken out in favor of the establishment of a thirteenth month pension for retirees.
The proposal was put forward by the unions and supported by the left, but strongly criticized by the right, the majority in the country.
As the country faces an aging population, voters also spoke out against gradually raising the retirement age from 65 to 66.