Under the "defined benefit" schemes, members receive a guaranteed, inflation-proof proportion of their wage, regardless of how well their investments perform on the stock market.
They're only really suitable for people in their mid 70s or older, because with many of these products you're locked into a fixed income that is not inflation-proof.
Savers who can not inflation-proof their wealth using conventional savings accounts may need to look elsewhere and take on more risk for greater returns.