If you can defer your state pension you get 1% increase for every 5 weeks- 10% a year. Best saving rate out there!
It's not a savings rate though. It's a gamble on how long you're likely to live for post-retirement.
Yes, you might get 10% more pension per annum, but you have to forgo 100% of your pension for a year to gain it. That means you would have to live for a minimum of 10 years post-retirement just to draw level with what you had to start with.
Admittedly, if you're convinced you're going to live until at least your mid-80s it might be worth considering, but it's certainly not a guaranteed moneyspinner.