A financial transactions tax could provide a lot of revenue to avoid austerity.

I am surprised by the idea of taxing derivatives less. Derivatives can destabilize the whole financial system, so it makes sense to tax them enough to discourage them somewhat.

Later: the explanation is that the tax on derivatives is stated as a fraction of the underlying assets, rather than the value of the derivative itself. Usually the value of the derivative is much less. I wonder, however, whether it is possible to create derivatives whose price includes the price of the asset and whether they would be a loophole.