I didn't remember that term before, but I do now.

It's a tax where the tax paid is proportional to income, i.e. 10 percent of $10,000, or 10 percent of a million.

Theoretically, payroll taxes are also proportional, but beyond a certain income limit, there is no additional Social Security tax. This is because benefits are limited too (a millionaire does not get 10 times the Social Security payments as someone who makes $100,000 a year). This makes a lot of people think SS taxes are regressive, and they certainly take a bigger bite out of lower income brackets, but the top 20 percent still pays 43 percent of our social insurance taxes. Which means even there, they carry a lot of the load for the lower brackets.

There is no upper income limit on Medicare taxes.

A sales tax with no exemptions would be regressive, in that necessities will always take a higher percentage of income from less wealthy people.

But all existing sales taxes have provisions that don't include necessities like food. In the case of flat taxes, proposals have included exemptions or some other provision to ease the hit on lower incomes. "Progressive" flat taxes. Go figure.

One plus of a consumption (sales) tax is that it requires no forms, no calculations, no hassle. I have to bare my soul to the IRS every year. God knows what would happen if their computers ever got hacked.

The real reason politicians don't like flat taxes, sales taxes, or other simple tax proposals instead of the current system is that the tax code is a major way politicians grant favors to friends and hand out punishment to their enemies. A good reason to enact such taxes, but the best reason it'll never happen.

Again, it's important not to get bogged down in the revenue end. As I pointed out, our problem is not insufficient revenue, it's too much spending.