£12,548 a year is real money you're choosing not to receive
The full new state pension is £241.30 per week — £12,547.60 per year. Defer for one year and you forfeit that entire sum. In return, you get approximately £728 per year extra when you eventually claim.
That's a 17-year payback. Defer at 67, claim at 68, and you don't break even until 85.
Look at that chart. The lines barely cross at age 85. If you die at 80 — which a significant proportion of the population does — you've collected roughly £4,000 less total pension. Die at 75 and you're out nearly £7,500. The entire deferral advantage only materialises if you're still alive and claiming well into your late 80s.
The deferral advocates focus on the percentage. Focus on the pounds instead. £12,548 is more than most people's annual ISA allowance. It's a new boiler, a year of council tax, or six months of food shopping. That's what you're giving up for a promise payable in 2043.