What can you tell about people by when they file their tax return?

Tax forms arrive around the beginning of the year and are due on April 15. That means there's a four-month treasure trove of data that social scientists and researchers could use to make various inferences about the type of person who files in January as opposed to an April filer.

First, look at the data.

The early filers: The Internal Revenue Service received 20,948,000 2001 tax forms between Jan. 2 and Feb. 8 of last year.

Lower-income taxpayers tend to file as early as possible, said Edward L. O'Hara, a Silver Spring financial planner, because they need the refund ASAP. Also, younger filers tend to hit the early window because their returns are less complicated, he said.

(Younger filers can use the new Form 1040(S)lacker, which can be summarized as follows:

("Step 1: Dude/Babe: How much cake did you make last year? Fill in number.

(Step 2: Look up that number in the gnarly tax table at the back.

(Step 3: Rock on -- you score a refund!/Bummer -- you still owe! What's up with that?")

Of course, there is another character in the first group -- the holier-than-thou filer. "Well, I just sat down with TurboTax last night and did our returns in two hours," Mr. Sanctimonious will drop into office conversation in mid-January, when everyone else is talking about the Super Bowl. His colleagues, full well understanding that there is no moral reward for early filing, quietly root for him to be audited. Painfully.

Between Feb. 9 and March 1 of last year, the IRS got 25,898,000 more returns, which joined those sent by the early filers.

From March 2 to March 31, the IRS received 25,716,000 returns.

So far, the data break down pretty steadily. About the same number of taxpayers file in January as in February and March, an average of about 800,000 returns per day.

The fun starts around April Fools' Day.

In the hectic half-month from April 1 to the Friday before the April 15 deadline last year, 18,034,000 panicked individuals rendered unto Caesar. That boosts the average up to about 1.2 million returns per day. Things are heating up.

Not to mention that thousands of these filers doubtless enjoyed the added benefit of having their procrastination broadcast to their community and the world, thanks to a journalistic convention that compels newspapers and television stations to send reporters down to the local post office at 11:45 p.m. on Tax Eve to interview the hapless. (Life's three certainties: death, taxes and annual stories about late tax filers.)

As the days ticked off during the week of last year's deadline (April 15-19), the IRS numbers become even more revealing, exposing what are surely deep character flaws in the American taxpayer's psyche and character. People get edgier. No doubt Ativan prescriptions spike around this time of year, as do neighbor-on-neighbor conflicts over unleashed pets that were amiably overlooked for most of the year.

The largest group of filers in the shortest amount of time are those who filed their returns at the deadline. During the week of last year's April 15 drop-dead, the IRS received 26,994,000 tax returns. That's about 5.4 million per day.

Among those who file late: Taxpayers who have Schedule K-1 forms coming from partnerships that they don't get until the last minute, O'Hara said, as well as the self-employed, those who don't need a refund and those who owe the government additional taxes.

Also, the very, very, very disorganized.

O'Hara said he has clients who present him with shoeboxes full of stuff, much of it superfluous to his tax-prep work. "I say, 'My goal is for you to take home more stuff than you leave with me,' " O'Hara said.

Then, there are the truly hopeless. They would deserve pity if they weren't such a reliable comic troupe.

"I'll have guys come in here at 4:40 p.m. on April 15 and I'll say the only thing you can do is file an extension," O'Hara said. "Which goes to August 15. Then, on August 15, they'll do the same thing, which takes them to October 15 and many times, the same thing will happen."