The data on wage gaps unveiled this week by Prof. Eugene Kandel shouldn't be surprising. After all, everyone knows that someone who studies engineering, computer science or business administration will earn much more than someone who studies political science, history or philosophy.

While the former earn about NIS 20,000 per month, the latter earn only about NIS 6,000. This isn't a secret.

Thus the angry responses from people who studied the humanities, Asian studies or social work were surprising. They were angry at the state, at the system, and of course at Prime Minister Benjamin Netanyahu, whom they assigned the chief blame for the fact that they earn so little.

I have unwelcome news for them: Look in the mirror. That's where you'll find the guilty party.

Anyone who chose to study something fun and easy to learn - something that, in essence, is a pleasant hobby - without thought for the negligible income it will produce, can only blame himself. Someone who wants to study the writings of Aristotle and Plato, or debate the results of the French Revolution, is obviously entitled to do so. But he would be wise to first acquire a sought-after, profitable profession. Otherwise, he is sentencing himself to low wages and continual discontent. And don't throw the exceptions at me.

If you study something for which there is no demand in the job market, you can't complain afterward that your salary is too low. It's also impossible to expect the state to employ all the college graduates who studied "whatever they pleased."

Granted, every field of study is important and honorable. But not all offer the same financial rewards. The public sector is important, too. It provides education, health, security, infrastructure and welfare. But it cannot absorb everyone who studied diplomacy or history.

The public sector's problem isn't a shortage of workers, but the opposite: It has a huge surplus of employees - whether we're talking about the Foreign Ministry, the Jewish Agency or the municipalities. Therefore, not only must we not add workers to it, we must reduce the number of public-sector employees and make the remainder more efficient.

Graduates of political science and Middle East studies departments who feel discriminated against must understand that a person's salary is determined by the value of his marginal output. An electrical engineer doesn't get NIS 20,000 a month for nothing; his work produces goods or services that are sold for high prices, which enables the owners of his company to pay him well and still earn a profit. If the owners could, they would pay him less. But demand for such workers outstrips supply, which is why he earns a nice salary.

Those angry young people must understand that they can't change the laws of economics. Kandel's team of researchers discovered, for instance, that the situation isn't exactly glorious in the life sciences, either. There's a large surplus of biology graduates, so their wages are low and some don't find work at all.

High wage differentials are a clear signal sent by the market's pricing system. That's how it informs us, with flashing red lights, what it pays to study and what it doesn't, based on the salary levels determined by the market. The current signal is loud and clear: It's worthwhile studying anything related to high-tech, engineering, computers and science - if, that is, you want a high salary.

This is also a national interest, because there is currently a clear need for graduates in technological fields: They are the economy's growth engine, producing revenues, exports, growth and employment.

But it turns out that only in a small proportion of high schools in the periphery is it even possible to study technological professions like computer science, physics and chemistry. That's a serious failure stretching over many years.

The Education Ministry woke up to this problem only two years ago. Now, it has decided that from this year on, high schools will be ranked not only by how many students pass the matriculation exams, but also on the "quality" of their matriculation certificates: The more students a high school has who studied the maximum five units in math, physics, computers, the sciences and English, the higher its ranking will be.

Once the high schools produce more graduates in the hard sciences and technology, these graduates will go on to earn college degrees in engineering, computers or technology. That will propel the economy forward - while also improving the state of their wallets.