* Biggest pension reform in two decades falls by 53-47 pct margin
* Retirement age for women stays at 64, men retire at 65
* Standard VAT rate will fall, not increase as planned (Adds official results)
By Michael Shields
ZURICH, Sept 24 (Reuters) - Swiss voters rejected raising women's retirement age to 65 in a referendum on Sunday on shoring up the wealthy nation's pension system as a wave of Baby Boomers stops working.
Authorities pushing the first serious reform of the pension system in two decades had warned that old-age benefits were increasingly at risk as life expectancy rises and interest rates remain exceptionally low, cutting investment yields.
But it fell by a margin of 53-47 percent, sending the government back to the drawing board on the thorny social issue.
The package turned down under the Swiss system of direct democracy included making retirement between the ages of 62 and 70 more flexible and raising the standard value-added tax (VAT) rate from 2021 to help finance the stretched pension system.
It sought to secure the level of pensions through 2030 by cutting costs and raising additional revenue.
Minimum pay-out rates would have gradually fallen and workers' contributions would rise, while public pensions for all new recipients would go up by 70 Swiss francs ($72.25) a month.
The retirement age for women would have gradually risen by a year to 65, the same as for men.
"That is no life," complained one 49-year-old kiosk cashier, who identified herself only as Angie. "You go straight from work to the graveyard."
Some critics had complained that the higher retirement age for women and higher VAT rates were unfair, while others opposed expanding public benefits and said the reforms only postponed for a decade rather than solved the system's financial woes.
Opinion polls had shown the reforms just squeaking by, but support had been waning.
The standard VAT rate would have gone up by 0.3 point from 2021 to 8.3 percent -- helping generate 2.1 billion francs a year for pensions by 2030 -- but the rejection means the standard VAT rate will now fall to 7.7 percent next year as a levy earmarked for disability insurance ends.
A 2014 OECD survey found Switzerland, where a worker earns over $91,000 on average, spends a relatively low 6.6 percent of economic output on public pensions. Life expectancy at birth was 82.5 years. More than 18 percent of the population was older than 65.
$1 = 0.9690 Swiss francs Editing by Toby Chopra