In reply to m0unt41n:
> If you expect to live for 20 years after retiring and you expect to work for 40 years then you have to save half your salary to have the same in retirement. Or save a quarter for a pension of half the salary.
Except that this isn't true either as it makes the huge (and historically incorrect) assumption that inflation and interest on your savings are equal as well as assuming that your living costs will be the same (which they almost certainly won't be with, typically, no children to pay for).
Actually, given our current economic system, any investment in a pension can reasonably be expected to be worth exponentially more than the capital amount that you save, with the a correlation between time 'saved' and the amount of gain.
The 'problem' today, in simple terms, is that people aren't seeing pension saving as a priority and therefore don't start until later in their lives than our parents generation which means the time for the savings to increase in value is shorter leading to reduced pension income.
Coupled with this is the fact, as you allude to, that owning a property is also becoming something that people do later in life so the pension 'top up' (in simple terms) of house selling / downsizing / reduced living costs is also reducing.
A complicated issue, compounded by the intricate ways in which all these types of financial instruments are interlinked, for example, pension pots provide a lot of capital for mortgages, means that it's not as simple as the maths you state in your post, nor the politics needed to amend it.
A blunt, and politically unpopular, argument would be that, if you live longer then you need to work longer. 60, or 65, as a retirement age is entirely arbitrary. Pensions, as they exist today, have only been around for 100 years or so and there's no reason why they should remain fixed in the timescales of 100 years ago.