>suggests that it is not true

I doubt this. See the HN post from a few days ago ("I put Mr. on my CV and got a job"). It would seem that employers not only pay their females employees less, but have little faith in them to get the job done, thus they wouldn't hire them in the first place.

The problem is that if the performance gap is imaginary while the pay gap is real, then someone could take advantage of the situation for enormous profit. If other employers falsely believe that some much more expensive hammers will be better at driving nails, that's great news for anyone who recognizes that the cheap hammers perform just as well--when 99% of my competitors are wildly deluded, there is the potential for profit.

Thus, we have two possibilities: either nobody in the world is both aware of the potential for arbitrage and unethical enough to exploit the situation, or the wage gap is smaller than these estimates suggest.

You're assuming that public image of said employers is unimportant, and that all employers are okay with being immoral. There's something to be said about companies with happy employees that don't feel like their employers are taking advantage of them.

There's nothing stopping employers from making the practical decision to employ underpriced women yet couch it in the rhetoric of feminism and diversity ("Diversity is important to us, and that's why we want to employ as many qualified women as possible.") This gets them a PR and economic benefit.

In fact, many new-economy juggernauts like Microsoft, Google, and Facebook do precisely this. Their employee marketing aggressively recruits women. Are they doing this out of the goodness of their hearts, or because they see an economic opportunity? Ultimately it doesn't really matter - the effect is that more women get employed in positions of power. But it's quite possible that the economic arbitrage that people are pointing out is happening in practice, right now, you just don't hear about it because most arbitragers are not dumb enough to let you know what they're doing. And the effect, over a long time scale, is that businesses run by bigots are replaced by businesses with a more accurate perception of personal productivity, which leads to a more equitable world for everyone.

There's no room for doubt, really. It does suggest that. It does not prove, so you can certainly doubt the conclusion, of course.

There really doesn't seem to be any alternative besides these three:

- Women are not underpaid or more efficient.

- There is not a noticeable number of unethical people seeking to get rich.

- People are getting rich by hiring lots of women and outcompeting everybody else who prefers men.

The last two don't look true to me, which suggests that the first one is true. I certainly could be wrong about the assumptions or conclusion, but it does suggest that.

You missed an option: There are "unethical people" that would discriminate for women to get rich, but for whom other prejudices against women are too strong, so they don't...

I'm not saying that this is the case, just pointing out that you missed options that would allow the hypothesised discrimination to exist.

it would be that All unethical people that would discriminate have other prejudices, which is implausible

You are oversimplifying by assuming that the supply of applicants for a given job is gender-neutral. I think it's generally accepted that one of the causes of the wage gap is that women are pushed toward stereotypically "female" careers, and those usually pay less.

These "unethical people seeking to get rich" could also outsource all jobs to third world countries and get their work done pennies on the dollar -- yet a lot of them don't. It doesn't look good for your company when you take advantage of people in plain sight.

> yet a lot of them don't

But many of them did...

The "third-world countries" equivalent would be: if third-world labor were cost effective, then people would be hiring labor in third-world countries and crushing the competition with their greater productivity per dollar, and getting rich in the process.

Which is exactly what happened over the past 30 or so years.

Other alternatives: - Most women do not like working in all-female workplaces - Competition from all-female workplaces run by ethical people

This is the link, for reference: https://news.ycombinator.com/item?id=6033567

It has been done.

> “[Alan] Greenspan explains his gender bias with the free market pragmatism that has become has hallmark. “I always valued men and women equally, and I found that because others did not, good women economist where cheaper than men. Hiring women does two things: it gives us better quality work for less money, and it raises the market value of women.”