It's hard to find good data on this. There are multiple dimensions to the problem, I'd like to focus on three: flops, non-volatile memory and RAM.

In case of my phone, Nexus 5, the triplet is (5 GFlops (estimated), 32GB, 2GB).

My initial research shows the point is somewhere in 60s, meaning there are people in the prime of life who were born then. I think the most interesting would be to see if this range shrinks or extends in time.