The article measures 'economic income' for a group of billionaires and demonstrates that billionaires pay a lower tax rate than the rest of Americans.

What is not addressed is how is the burden of paying the societal cost of running the government shared?

Currently, the answer to that question is that the tax system is designed such that the only people who pay for the annual cost of government are those with income.

And there is a huge difference between people who must earn a wage in order to survive and a billionaire. People who must work to survive have no choice about paying taxes.

However that is not the case of someone with a net worth of a billion dollars. Anyone with a billion dollars only earns a taxable wage because they want to, not because they must do so to survive. Likewise, they only pay taxes on interest or dividends because they choose to own assets that pay taxable interest and dividends. And only pay taxes on taxable profits from the sale of stock or other assets because they choose to own such assets - and then decide to sell.

Any billionaire could choose to hold their money in a manner that generates zero taxable income. The truth is, a billionaire chooses how much taxable income he/she decides to have each year. Very unlike working Americans.

Moreover, the burden of the money contributed in taxes by a billionaire versus the burden of the money contributed by those who work, is not even comparable.

Viewed as a percentage of total wealth paid each year, it would be very difficult to argue the burden of contributing to the annual cost of running the government is being shared fairly.