The figures give the first indication of how well the Government's landmark auto-enrolment scheme is being received.
Auto-enrolment started with the largest employers in October last year and will extend to the smallest firms by 2018.
It was introduced to address chronic under-saving with millions not putting aside enough for retirement, and only 1 in 3 private sector employees paying into a workplace pension.
The research of the UK's 50 largest employers shows that on average just 9% of people have opted out.
The findings also suggest that young people are leading the way in the savings revolution, with more under 30s staying in a pension scheme than other age groups.
Minister for pensions Steve Webb said the low opt-out rates bode well for the "ambitious programme".
"Too few people have been saving for retirement. It is all too often something to be put off, something for tomorrow," Webb said.
"These figures show that people really value the chance to save into a workplace pension as they know they will also get money from their employer and the taxman too."
He added: "The sooner people start a pension the better, and this report shows that young people are keen to take charge and plan for their future."
