Expanded consumer credit, and it's appurtenant high interest rate cost, would tend to keep young people less wealthy towards the last half of last century. As credit card debt skyrocketed, savings rates plummeted from almost 11% in 1982, to 1.5% in 2007 [0].
Similarly, the power of 401(k) investing is really only coming into it's own in the last decade or so, since 401(k) accounts have had 30 years to mature, total retirement assets now total well over $3 Trillion nationally.[1]
[0] http://www.americanhistoryusa.com/give-me-liberty-or-give-me...