Given that lots of other things have changed in society, if this gap has stayed the same as an average or median on the whole, that is speaking to something deeper. So what, exactly?
Thomas Sowell makes the point that average ages vary by race: https://www.tsowell.com/spracecu.html and there must be other factors, like where races live. Asians being based in San Francisco pre Silicon Valley's boom has surely had a positive affect on their collective income and wealth.
I really wish there was a clear cut answer, but there self evidently isn't one, unless we believe that every change in society in the last 50 years was made for cynical reasons. So there must be all sorts of answers in the data, sliced properly, that could lead us to a more equitable future.