When it comes to wages, we are all experts, able to effortlessly zero in on the one and only fair number both for ourselves and for our co-workers.

Strangely enough, we are always underpaid. Our co-workers are too, assuming they actually make less than we do, and don’t snatch that last clean coffee mug. 

Perhaps this is why it has become so fashionable to analyze wage disparities between social groups, be they men and women, whites and blacks, locals and foreigners. Only the left-handed jugglers still don’t know how they stack up against hearing-impaired acrobats.

Sometimes, the wage differentials point up underlying inequities caused by longtime discrimination. Sometimes, they only show that two randomly chosen statistics don’t precisely match. But such comparisons can never escape a fundamental truth: everyone pays, and earns, what the market will bear.

So it is hardly surprising that Ukrainian employees resent the higher wages earned by their Western co-workers, as Post reporter Tiffany Carlsen reports this week in a front-page story. 

What is surprising is that no Western employer was willing to put his name to this basic truth: Ukrainians make less because they are willing to work for less. Given their options in this slumping economy, that’s hardly a surprise. 

Most local workers lack some of the skills of their Western colleagues. But even those who can match Western credentials and productivity end up making less, because unlike their Western counterparts, they usually are precluded from competing for jobs outside Ukraine. 

They are the exception to the rule that pose the only genuine dilemma faced by Western employers. Do you let the market drive down the compensation of a Ukrainian worker who is at least as useful and productive as a better paid foreigner? Can the free market be the only judge of worth? 

The answer here is, not quite.

Since most businesses appear to lose the power of speech when it comes to discussing wage differentials, we will come out and admit that a couple of our Ukrainian employees now hold jobs exactly like those of Westerners except that they pay less. 

They have been told that the situation is temporary, because they are more valuable to us in the long term than an expatriate with an expiration date stamped on his visa.

In the end, what matters to most of us is productivity, not the color of someone’s passport. We suspect most rational employers feel the same.

Already, Western companies are paying a premium for the best workers Ukraine has to offer. What’s true for them will eventually be true for the nation as a whole: shortly after they match Western productivity, they will begin to earn comparable pay.

In the meantime, the disparity in wages ought to make them strive harder, not gripe louder.