From the Institute for Fiscal Studies:
Inherited wealth looks like the only major factor that could act to make individuals born in the 1960s and 1970s better off in retirement than their predecessors, on average.
When compared with those born a decade earlier at the same age, these cohorts: have no higher take-home income; have saved no more of their previous take-home income; are less likely to own a home; probably have lower private pension wealth; and will tend to find that their state pensions replace a smaller proportion of previous earnings.
These are among the main findings of a new report by IFS researchers published today, funded by the Joseph Rowntree Foundation, the IFS Retirement Saving Consortium and the Economic and Social Research Council.
I've not read the full report, I assume that they also mention some of the causes: insanely higher rents and house prices, higher levels of tax on output and employment, tuition fees etc etc.