@rysiek @baldur The concepts go way back to at least 1776 in The Wealth of Nations:
> A key requirement for effective labour arbitrage is that the employees can be treated as interchangeable, well, components. Jobs that require expertise lend themselves less to arbitrage than jobs that don’t.
"Secondly, the wages of labour vary with the easiness and cheapness, or the difficulty and expense, of learning the business.
[...]
When any expensive machine is erected, the extraordinary work to be performed by it before it is worn out, it must be expected, will replace the capital laid out upon it, with at least the ordinary profits. A man educated at the expense of much labour and time to any of those employments which require extraordinary dexterity and skill, may be compared to one of those expensive machines. The work which he learns to perform, it must be expected, over and above the usual wages of common labour, will replace to him the whole expense of his education, with at least the ordinary profits of an equally valuable capital. It must do this too in a reasonable time, regard being had to the very uncertain duration of human life, in the same manner as to the more certain duration of the machine.
The difference between the wages of skilled labour and those of common labour, is founded upon this principle." (Book I, Chapter X)
Labour arbitrage: "What are the common wages of labour, depends everywhere upon the contract usually made between those two parties, whose interests are by no means the same. The workmen desire to get as much, the masters to give as little, as possible. The former are disposed to combine in order to raise, the latter in order to lower, the wages of labour. [...] There are certain circumstances, however, which sometimes give the labourers an advantage, and enable them to raise their wages considerably above this rate, evidently the lowest which is consistent with common humanity.
When in any country the demand for those who live by wages, labourers, journeymen, servants of every kind, is continually increasing; when every year furnishes employment for a greater number than had been employed the year before, the workmen have no occasion to combine in order to raise their wages. The scarcity of hands occasions a competition among masters, who bid against one another in order to get workmen, and thus voluntarily break through the natural combination of masters not to raise wages."