Illegal migrants in particular have responded to the slump: in the past year or so the stock of unauthorised migrants has stopped rising.
But in 2010, according to a recent report from the Pew Research Centre that counts both authorised and unauthorised migrants, Asians were America's biggest migrant group.
The bad news there, however, is that state crackdowns on unauthorised migrants, along with a border that is getting harder to cross, are making it tougher for migrant workers to flow to where they are needed.
So "The current strategy of border enforcement is keeping more unauthorised migrants in the US than it is keeping out".Tighter controls in Europe are probably creating similar incentives to stay rather than to commute or return.
A critical mass of Republicans in Congress may be swinging behind a "Dreamer" law, which would allow unauthorised migrants brought to America as children a fast track to citizenship if they meet certain conditions, such as getting educated.
Under May's leadership, the Home Office has embraced the idea of creating a "hostile environment" for unauthorised migrants; and it was on her watch that those infamous Home Office vans cruised the streets of six London boroughs – a move even Nigel Farage said was "nasty", and that the Home Office quickly abandoned.
In 2014, deep in the Indian Ocean and away from public view, one of Australia's Commonwealth vessels detained unauthorised migrants for 1 month.
As distinct from Hirsi and M70 with the CPCF case, the High Court of Australia held that detainment at sea for the purpose of preventing arrival of unauthorised migrants to Australia and push back to safe port was lawful.
While the judges were considering the CPCF case, the Australian government passed a number of amendments to the Migration Act and to the Maritime Powers Act in December 2014 to allow for the removal from high seas of unauthorised migrants without breaking national laws.
Then there are the criminal networks to which unauthorised migrants are particularly vulnerable on their way in (or out) of the country.
