Senior moment.

MY SISTER WARNED ME ABOUT THIS nearly four years ago, but she couldn't soften the blow. No amount of ignoring the problem, or exercising, or listening to hip new music -- nothing -- could alter a simple fact: I got my letter. The letter.

If you have to ask, then you're still under 49. I have actually conducted an unscientific poll to prove this point: I told just about everyone I know that I got "the letter," and if they were my age or older they knew immediately what I meant.

If they were younger they had no clue.

"The letter" in question is the one from AARP. Not "aarp," pronounced like its own word. Nor is it, any longer, the "American Association of Retired Persons," although the group retains the copyright on that phrase.

No, it is simply AARP, pronounced, their press literature insists, A-A-R-P, the nonprofit organization that frightens the bewillikers out of everyone about to turn 50 and all members of Congress.

They're gray. They're powerful. They're not afraid. And now, as they say, whether I join or not and whether I like it or not, they are us. Or rather, me.

My generation has had an enormous effect on this country right from the start. The so-called Baby Boomers, born between 1946 and 1964, are by far the largest generation ever born in the country (The peak year was 1952, the year I was born.) To accommodate all of us, more schools were built, more dormitories at colleges were constructed, more of everything was provided.

We were the rock 'n' roll generation, the first TV generation, more mobile than any generation in history, and, above all, we took pop culture and consumerism to sometimes ridiculous heights. Whether the "Greatest Generation" just ahead of us, or the Gen-Xers behind us like it or not -- and whether it is for good or ill -- my generation is still figuratively booming. It will, for quite some time yet, wield enormous influence on society at large.

When we were young we demanded social change and in large part got it. That isn't going to change; only the issues are going to be different.

We are aging -- the oldest among us are approaching 60 -- and looking retirement square in the face. The issues now coming to the fore are health care, Social Security reform and survival, and shorter-term investments.

And the truth is that we, as a group, are woefully unprepared for what lies ahead. We haven't saved, our pensions and pension-like instruments haven't been as important as our day-to-day hedonism, and we are destined to be unbelievably cranky about the ill effects of growing old.

Oh, yeah -- and we'll live longer than any other generation since the dawn of time.

The good news is that we are -- better late than never -- beginning to understand the error of our ways. In the next 20 years we'll be working hard to make up for lost time, so, as usual, we're going to be a great market for companies and entrepreneurs who can meet our needs.

I'm sure I'll eventually adjust to being a senior.

Just give me a moment.