Part of the argument here is that the top 1% has access to investment classes that have high yields and and which are not available to the remaining 99%.

There is one obvious, government mandated reason that the 99% don't have access to high-yielding investments such as hedge funds: Investors in these funds are required to be accredited investors. This means they must be already wealthy by law. For example, while researching I've found a hedge fund that makes small business loans and yields 11% with no risk to capital. But in order to invest, one must be accredited, which means they have $1,000,000 of net worth outside of their home equity, or, have earned at least $200,000 household income in each of the last 2 years, or, have earned at least $300,000 last year. So by law, the 99% (I am using that term somewhat loosely here) is not legally permitted to take advantage of high-yielding opportunities.

Thanks to the Web and Internet tech in general, opportunities are becoming available. For a $2,500 minimum, any investor can put money into peer lending and earn >10%.

But I believe what really separates the 1% from the 99% is financial knowledge more than anything else. It's actually a pretty involved effort for the majority of the population to become wealthy. Involved in that there is a lot that needs to be understood about earning, budgeting, saving and investing. That knowledge then needs to be applied for the long term (decades), and then one must hope that there is no divorce, illness or major college bills that can derail a well-run effort.