Immigration

[Urbane Guerrilla]

. . .it is the rich who employ the Mexicans, and the Plantation owners who stand to profit the most from an entire underclass of indentured servants for whom they have to pay zero benefits.

That is, the total cost of employment of such employees is low. A too-great total cost of employment means less hiring and more joblessness. See the 15% unemployment rates over in Europe for a textbook example.

The opposite case, of course, means maximum employment, though it doesn't necessarily do much by itself for greater pay.