Reason has an interesting article by Kerry Howley titled: Open Markets, Closed Borders . It cites a study of the Irish Potato famine where Irish immigrants fled to the United States and effectively relieved the pressure of what was a failing Irish economy while feeding the demands of a burgeoning US labor market.

The article states that since the migration wave from the famine that it has taken the Irish population 200 years to recover and real wages did not fall following the disaster. This is a similar economic process to the freed convicts in Australia who suddenly found themselves in a very tight labor market courtesy of limited migration to Australia. That colonial scarcity led to many eschewing the labor market altogether and becoming self-employed.

It is a sad fact that nation-states are clinging to their power through appeals to nationalism and clogging up the labor and market flows with poor policy designed to stop economic osmosis at the political boundary of the nation-state. The article writes:

Where once moving in meant showing up, the process of emigration has become bureaucratized, escape valves shut tight. Imaginary lines have hardened into often impassable borders, labor markets sharply curtailed.

Europe is not replacing itself, but it is harder to enter; developing countries cannot sustain their bulging populations, but they are harder to leave.

The article also notes that the free movement of goods and capital under globalisation has not been met with the free movement of labor. Despite this increasing numbers of individuals are joining the global workforce. Australia is a good example; it is estimate that the Australian Diaspora is approximately 5% of the current population.

One truth is that where politics does not provide or prohibits, then people will find a way around it:

The [immigration] bill fails to tap into the huge potential of the U.S. and developing world for mutual wealth creation; that's a potential employers and illegal immigrants will continue to discover themselves, outside the formal economy. Which means that we'll soon be having this debate again.

The fact there is so many illegal immigrants in the US means the labor market is broader than what politics or legislation defines it to be.