It's a tough question. It's a question that has been looked at somewhat in literature.
What we know for sure is that as your income goes up, you are more sensitive to a tax rate change. Clearly that's what studies are telling you.
The second thing is that we know the reaction is coming from two channels. The first one is you may work less, so that's the real economic effect of it. The second channel is that you may be a bit more aggressive in your tax planning. The key question is how do you distinguish between less work effort and tax planning? There are a number of studies out there that use techniques such as comparing elasticities using gross income, so not your taxable income, but before deductions and everything. It's suggested it's less of a planning versus the elasticity of the taxable income. The suggestion is that there is less elasticity when you use gross income as opposed to taxable income. We suggest that potentially the tax planning channel is more important than the less work effort channel.