The statistic comes from the 2017 Survey on Payment Methods from the Swiss National Bank, published on May 31st, 2018.
The report looks payment behavior and the use of cash by households in Switzerland and uses data gathered from an interview survey with around 2,000 Swiss residents.
According to the findings from the Swiss National Bank report, cash is used for 45% of household payments in Switzerland in terms of value of transactions (SNB, 2018).