Around 350 economists from around the world have written an open letter to the G20 governments for a tax on currency speculation transactions. The text of the letter is:

Dear G20

As economists from across the world, we call on you to implement a financial transaction tax (FTT).

This tax is an idea that has come of age. The financial crisis has shown us the dangers of unregulated finance, and the link between the financial sector and society has been broken. It is time to fix this link and for the financial sector to give something back to society.

Even at very low rates of 0.05% or less, this tax could raise hundreds of billions of dollars annually and calm excessive speculation. The UK already levies a tax on share transactions of 0.5%, or ten times this rate, without unduly impacting on the competitiveness of the City of London.

This money is urgently needed. The crises of poverty and of climate change require an historic transfer of billions of dollars from the rich world to the poor world, and this tax would offer a clear way to help fund this. Given the automation of payments, this tax is technically feasible. It is morally right. We call on you to implement it as a matter of urgency.

It is being called a Robin Hood tax, and seems to me to be a good idea. As long as the money does go to fighting poverty and climate change.