Liberals should care about global welfare.
While global welfare would increase, they might lose.
The ultimate aim is to assess the impact of migration on global welfare.
Now examine Osborne's claim that Britain has "7% of global welfare spending".
In his model, this would have only modest effects on global welfare; but how confident can we be of that?
In May, the Copenhagen Consensus, a group of respected economists, produced a list of the best ways to spend a notional $75 billion on improving global welfare.
But such a drastic reduction would produce a slump in world trade the two economists reckon global welfare would fall by 1%.
And it is absolutely right to say that this trend is hugely important and is contributing to a massive rise in global welfare.
And as he waspishly noted, "If risk-making were a value-adding activity, Russian roulette players would contribute disproportionately to global welfare".
If it is global welfare you care about, especially the welfare of the poor, international meetings come no more important than this.
As a result, taxes were far more desirable than permits, yielding $337 billion in global welfare gains versus only $69 billion for permits.
