Geneva - Swiss voters on Sunday rejected a divisive pension reform plan that the government said was vital to safeguard benefits, according to initial estimates.Figures released by the GfS Bern polling institute shortly after polling closed, showed that 53% of voters said no to changes to the current system which would have raised women's retirement age by a year to 65 as well as hiking VAT to help fund benefits. Only 47% of voters cast ballots in favour of the reform, which was approved by parliament in April. Ahead of the vote, opinion polls suggested the result was too close to call, with the pro-reform side slipping marginally in recent weeks.With most voters casting their ballots by post, final results are due out later on Sunday.The government said the changes would help avoid deficits in a social security scheme facing pressure from an ageing population, with baby boomers entering retirement. Rising life expectancy, now 83 years, has added further strain. But critics argued that the changes were too modest to rescue a retirement system in financial peril.The vote is the latest in Switzerland's direct democracy system, which includes four referenda a year on major national issues.Irrational voting behaviour? Backed by leftwing and centrist parties, the reform proposal also includes more retirement age flexibility and increased contributions from employers and workers.The plan, officially known as Pension Reform 2020, will only come into force if voters also approve the corresponding VAT increase.Support for the plan stood at 53% in mid-August but had fallen to 51% days ahead of the vote, while just 50% of respondents said they backed the VAT increase.The co-director of GFS Bern, Lukas Golder, had told public broadcaster RTS that there may be "irrational voter behaviour", where people approve pension reform but reject the VAT increase needed to fund the system. Rightwing parties campaigning against the move say it does not guarantee the survival of the pension system after 2027 and that beyond that date, future generations will be forced to come up with yet another rescue package.Because the VAT increase requires a change of Swiss constitutional law, it needs double approval to pass, including majority support among voters and majority support in more than half of the country's 26 cantons.