Over the last 24 hours, much has been written about Mitt Romney's surreptiously recorded comments about the 47 percent of Americans who pay no taxes, and what he believes that says about both their proclivity to vote for President Obama and their sense of personal responsibility.

But here's something I haven't seen, perhaps because relatively few Americans -- the pundit class included -- have a full understanding of the concept of marginal income tax rates. The fact is that under IRS regulations, 100 percent of American families of four -- not 47 percent, but 100 percent -- pay no taxes on their first $26,000 of income. To put that number in perspective, it is just slightly above the income level established as the federal poverty guideline for a family of four, which is $23,050.

Here's why no family of four pays taxes on that first $26,000. Each such family gets a $3,650 personal or dependent deduction for each family member. When you multiply that by four, you get $14,600. In addition, each such family gets at least the standard deduction, now set at $11,400 for those married and filing jointly. Families with higher incomes that have mortgage payments and property taxes to deduct, of course, can itemize deductions and are thus able to deduct a higher amount. But all families can claim at least the standard deduction.

Add those two deductions together -- $14,600 in personal and dependent deductions, plus the $11,400 standard deduction -- and you get $26,000. Thus, whether their income is $26,000, or $260,000, or $2.6 million, no family of four pays any taxes on their first $26,000.

If they make $26,000 or less they pay no taxes. If they make more than that, they pay taxes only on the amount above that. Those deductions are not a handout, and they are not special treatment for anyone. They are standard tax policies that apply even-handedly to all taxpayers.

Wherever folks choose to take the discussion about tax fairness beyond that, it should start with the understanding that no family of four pays any taxes on that first 26 grand.