I believe they're at the point, or will be if they can stay relevant for long enough, where they can have a good stab at our future before we know anything about it.

n% of 20-something year old Billys facebook Saturday statuses mention 'pub', 'hangover' and 'pint' between 2000 and 2330. Therefore chances are that Billy will be in the pub every week in between those times.

x% of Billys family had photos of them being grey haired at 55, therefore Billy is likely to go grey at about the same time.

n% of Billys friends had taken photos of babies by age j after being in a relationship for k years. Billy has been in a heterosexual relationship for x years therefore is m% likely to have a child at a similar age.