One of the main purposes of the wealth tax is not to raise funds. The tax described in the book would be quite low, below 1%. Remember, the rate of return on

One of the main purposes of the wealth tax is not to raise funds. The tax described in the book would be quite low, below 1%. Remember, the rate of return on fortunes over a million Euros (below this, they wouldn't be subject to the tax) is around 5%. So this does little to slow the global concentration of wealth. The main purpose of the tax is to track this wealth. When Piketty did research on the fortunes of the very wealthiest individuals, he had to rely on estimates from Forbes magazine, whose methodology is far from scientific. The idea is that with a better public understanding of where and how wealth is concentrated, we can formulate better policy.