Theresa May created a shortage occupation list as a key feature of her drive to reduce net immigration to the tens of thousands.
Clamping down on skilled work visas for people from countries outside the European Economic Area by imposing a 20,700 annual cap was part of her overall strategy. But it meant there had to be enough flexibility in the system for in the event of the cap being reached and there being skill shortages. The shortage occupation list was her answer, and it was a pretty rigid instrument.
Inevitably it has involved a huge amount of bureaucracy with officials having to gather evidence on employment levels, salaries and applications across the economy before deciding what should be put on it, or taken off
