The "bottom 30%" of the population has *ALWAYS* had a net worth that is pretty much zero.  So multiply nearly zero by 10 million and you still end up with nearly zero.  Hence this statistic is rather meaningless.

Remember that this is looking at total assets.  What assets do most university students have?  Maybe a car if they are lucky, though chances are they have student loans.  Same goes for new grads.

Having a low, zero or even negative net worth is not necessarily a problem though. Fresh out of med school?  You might be earning $150,000/year or more but your assets are likely less than your liabilities giving you a negative net worth.  10 years into the future though and that picture is going to look VERY different.

Keep in mind that net assets has a very close connection with age.  Someone with the median net worth for people age 55 to 65 would probably fall into the top 1 or 2% of net worth for people age 18 to 29.