Some research on Mexican immigrants and unemployment rates summarized here.
This is the paragraph I find most interesting:
But there are many reasons why Mexican immigrants are quicker to react to changes in demand for their labor. One reason for their mobility is that they usually do not have or are not eligible for Unemployment Insurance (UI) and other social safety net programs, and so are completely dependent on the wages they earn.
If you pay people not to work, then people don’t work. The converse is also true: if people earn no money unless they work, then they’ll work. Seems simple. Yet, some people seem utterly incapable of understanding this.