how the rich get richer

from the 1940s through the mid-1980s, the richest one person [that should be one percent] got a much smaller portion of the whole:

That lasted until the late-1970s — and you saw what happened from then on. It's what economists call "The Great Divergence," or a great increase in wealth inequality.

So, what caused this?

Wealthy people began making more of their money from investments and business income

Everyone else continued to make money on salaries and wages.

But since the 1970s, we've significantly reduced how much we tax investment income

The most we've taxed investment income is about 40 percent. That was in the late-1970s. Since then, rates have been much lower. In fact, until 2013, the most investment income could be taxed was 15 percent. It's now about 25 percent.

Keep in mind that, if you're filing as a single person, your salary and wages starting at $38,000 are taxed at 25 percent — and from there the rates only go up.

Since it's the rich who made more and more money on investments, taxing investments less helped them a lot.

American tax and transfer policies are among the worst in reducing inequality, compared to other developed countries

Even though we have a relatively progressive tax system, we now have some of the lowest tax rates in decades. Low tax rates mean the US collects less revenue — and can transfer fewer resources back to taxpayers.