With the November elections approaching, there is much political talk (I could call it something else, but I am writing for a family newspaper) about the income tax. Candidates and commentators throw around revenue projections, tax rates, and statistics like so much confetti. I am not sure they know what they are talking about, but I want to make sure you do. Here are definitions of some commonly used terms.

Average Tax Rate – The rate a taxpayer would be taxed at if taxing was done at a constant rate, instead of progressively. It is calculated by dividing the total tax paid by income.

For example, the first two tax brackets for single persons in 2011 are 10% for everything up to $8,500, then 15% for everything between $8,500 and $34,500. Adjusted Gross Income (AGI) is the number at the bottom of page one and top of page two of the 1040 form. Taxable income is AGI minus deductions and exemptions. If taxable income is $20,000, then the tax is $850 (10% of the first $8,500) plus $1,875 (15% of the next $12,500) for a total of $2,750. What is the average rate? The total tax of $2,750 is divided by total taxable income of $20,000 which gives an average tax rate of 13.75%.

While this example is clear, it is not at all clear what number should be used here as "income." Is it the AGI? Is it taxable income, which would drive the Average Tax Rate up? Is it adjusted gross income plus tax-exempt interest, non-taxable social security, and other non-taxable items which would drive the Average Tax Rate down? What is total tax? Intuition dictates it is the tax due on the 1040, but some analysts add all other taxes paid (see the Debbie Bosanek example below), driving the Average Tax Rate up. When commentators and politicians throw average tax rates around, it is impossible to know if they are comparing apples to oranges because the calculation of the average rate is not made consistently. Beware.

 Effective Tax Rate – This term is not used consistently. Some use it to mean exactly the same this as Average Tax Rate. Others use it to describe the amount of tax a taxpayer pays when all other government tax offsets or payments are applied, divided by total income. For example, the Congressional Budget Office refers to an effective federal tax rate on individuals which includes all benefits received including things like health care and food stamps, and all four of the major federal taxes – individual and corporate income taxes, payroll taxes (social security medicare, etc.) and excise taxes (like cigarette tax).

 Marginal Tax Rate — The amount of tax paid on an additional dollar of income. The marginal tax rate for an individual will increase as income rises and higher brackets are passed into. In the above example, lets assume taxpayer made $12,000. What is his marginal rate? He has passed through the $8,500 bracket and the next $3,500 of income is taxes at 15%. If he makes another $1 of income, it will be taxed at 15%. The taxpayer’s marginal rate is 15%.

Have you heard people saying they don’t want to be in a higher tax bracket because they will pay more tax? This statement is based on a misunderstanding.

Lets look back at our example taxpayer. If he makes $20,000, his marginal rate is 15% and he is in the 15% bracket. It is important to understand that just because he is in the 15% bracket, that does not mean that all of his income is taxed at 15%. It just means that the next dollar earned will be taxed at that rate. Going in to a higher tax bracket does not raise the tax on all of the income below that bracket. Moving into a higher tax bracket is usually not a "big deal" although many folks talk about it as if it is a tax disaster. It is a complete myth that going into a higher tax bracket costs you money. A progressive tax system only imposes the highest rates of tax on the incremental dollars over the top of the last bracket.

There has been much talk about the Buffett rule. Warren Buffet pointed out that his secretary, Debbie Bosanek, pays a higher rate than he does. ABC reported Bosanek’s tax rate as 35.8% in payroll and income taxes (higher than even the top income tax rate), while Buffet’s is 17.4%. They are talking about the average rate, that is, total tax divided by total income. We don’t know the details but we can surmise that most of Buffet’s income comes from capital gains and qualified dividends, both taxed at a maximum rate of 15% while the secretary’s income is taxed at ordinary income tax rate and his numbers include her payroll taxes, both employee and employer. There are lots of other factors, too, like charitable deductions, that we really can’t quantify without seeing the actual tax returns.

Last Monday, the Senate blocked a vote on the Fair Share tax – referred to as the Buffet rule. The Fair Share tax would have required people with income offer $2 million to pay at least 30% in income tax. It didn’t pass and spawned a whole raft of articles, talk shows, and blog posts – all throwing around average, effective, and marginal rate lingo – often incorrectly.

The Bush tax cuts expire at the end of this year. You can expect to hear a lot about brackets, rates, and income from the lame-duck Congress in the seven weeks between the November 6 election and the end of the year. What will be the state of the economy and who will win control of the House, Senate and White House? No predictions here. My crystal ball is broken.