Some academic economists have suggested that countries institute a small tax on all foreign exchange transactions, a so-called Tobin tax after the economist who first proposed it, in order to discourage speculative capital flows. But very few policy-makers give such a tax any chance of BIS Review 11/1999  – 12 –  being implemented and, if implemented, of actually working as intended.
To be effective, it would need to be applied in all countries at the same rate, lest foreign exchange transactions simply migrate to a country where the tax is not applied.