All things being equal, hundreds of local women will gather tomorrow in Market Square to protest the fact that all things are not equal.

If the rally held in Harrisburg on April 8 is any indication, these women will protest the "fact" that we females earn only 77 cents for each dollar earned by a man.

Or if last year's Equal Pay Rally in Market Square is the standard, they will decry the "fact" that women earn only 69 cents on a man's dollar.

Or maybe it's the 80 percent alleged by a high-profile study from the American Association of University Women last year.

Why the different numbers? Apparently, as Teen Talk Barbie once complained, math is tough.

Either it's too hard for women's advocacy groups to master, or it's their devotion to ideology that prompts them to protest, year after year, an outrage that the math indicates may not actually exist.

Whether sloppy or dishonest, it's enough to make some of us women embarrassed for the sisterhood.

Giving credit where it's due, it was the work of women's advocates that so greatly broadened the career opportunities available to women of my generation. Civil rights legislation of the 1960s and '70s made it illegal to refuse us admission to higher education, to keep us out of "unsuitable" professions and to fire us if we became pregnant.

But almost as long as these options have been possible, women's advocates have been protesting that women are not earning anywhere near as much as men.

And for just as long, economists and researchers who are not tethered to any movement's ideology have been pointing out how misleading these claims are. Time after time, the research has shown that when we take into consideration career choice, length of employment, time in and out of the work force and number of hours worked, the wage gap disappears.

The latest and most often cited salvo in this ongoing exchange is the 2007 AAUW study, "Behind the Wage Gap." The organization's news release and the many articles it provoked all report that one year out of college, women earn only 80 percent of what their male counterparts earn, "even when they work in the same field." Ten years later, we're told, it's down to 69 percent.

Read on a bit farther, and you find that after adjusting for the usual important factors, the wage gap is only 5 percent. And if you read the full report, you'll learn that men's and women's earnings are compared within a given field but not by specific job, and are compared without accounting for how many hours each person worked.

Since the study also finds that one year after graduation, men work 7 percent more hours than women, even a casual reader might wonder whether there's any gap at all -- much less whether women are suffering from discrimination.

But the wage gap that exists before we do the math exists because -- despite 40 years of hard-line feminist rhetoric trying to change how we think and feel -- women still tend to choose careers that allow flexibility for bearing and rearing children.

At the Harrisburg rally earlier this month, state Sen. Jane Orie, R-McCandless, cited the 77 cents-on-the-dollar figure, and state Sen. Michael Stack, D-Philadelphia, bemoaned, "This pay disparity doesn't just hurt women themselves, it also hurts their families."

That's exactly backwards. The pay disparity exists because we stubborn women keep putting our families ahead of our careers.

And there are ways for society to acknowledge the importance of our choices that transcend dollars and cents.

Last year's Equal Pay Rally was followed immediately by a summit between organizers and local leaders, chaired by The Heinz Endowments' then-president Max King, to discuss how local corporate boards and government entities might increase their paltry numbers of women.

Notice the cognitive dissonance in the two goals of the Equal Pay Rally: If women were just like men and made the same choices men make, it wouldn't matter whether men or women served on local boards or in government.

But the very priorities that often motivate women to follow career paths different from most men are the same priorities that activists feel would add so much to local leadership.

Women's advocates cannot logically have it both ways at once. But to further a political agenda that many women do not share, the ideologues try to keep us stirred up with baseless complaints. They need a mass of us to give their agenda weight.

But the measure of our progress is that each of us gets to decide which way and how far to go. These days it is our individual abilities and choices, not institutionalized discrimination, that nudge the journey this way or that.

We've come a long way, baby, and the facts prove it.