While Henry did link to his Australian article this morning I want to draw attention to one of his final paragraphs:
A simple calculation is telling. Assuming no behavioural change, raising the top marginal rate from 46.5 per cent to 49 per cent for those earning above $180,000 would increase annual income tax collections by about $1.2 billion. However, if the response in Australia parallels that in Britain, instead of rising, taxes collected from top-income earners could actually fall by up to that amount. Nor is it difficult to see why: 30 per cent of the top taxpayers in Australia are 55 or over, so are making choices about how long to continue working; nearly a third are in occupations which have substantial discretion over the timing and form of income; and a majority have sources of non-taxable income which offer opportunities for rearranging tax liabilities. But while reducing the tax take, all those adjustments impose steep economic costs, with each dollar raised shrinking national income by at least 50c.
Symbolism is expensive and counter-productive.