Oh come on... why 70%? Presumably retirees don't have childcare costs, can downsize on housing, no more daily commute so savings on transport and lunch costs, ... Also, does "private savings" account for accumulated housing equity?
Also, I think that "retirement savings" are a fundamentally misguided economic policy... There's a fixed amount of wealth created at any moment (and a lot of it isn't transferable over time - in particular, labor, energy and food), so by "saving for retirement" we're actually causing a deflation (less money spent to buy same amount of wealth) and will cause an inflation when we start "spending retirement savings" (more money spent to buy same amount of wealth, so prices go up). This is a rat race, you only get ahead as long as you save more than others (similar to the housing bubble). The only sustainable solution is the working population to subsidize the non-working population (kids, students, retirees) in real time, year by year. If that math doesn't work out, we need to change it (make more kids who become new workers or make less retirees by having people work longer). Or post-scarcity economy of course.