Someone forgot to model growth in the value of the asset, and/or putting the wealth to use. A wealth tax is, to an approximation, the equivalent of the "management fee" that an ETF charges, but with the revenues going to the government. If you have a bucket of money that isn't doing anything, then what value does it actually bring to the economy? Penalizing static value seems almost reasonable.
>If you have a bucket of money that isn't doing anything, then what value does it actually bring to the economy Wealthy people don't just leave their money under a mattress, they invest it in something. Even if they just left it in a bank, the bank is still going to lend that money out and invest it. Taxing wealth just encourages riskier investments, as higher risk is needed to achieve comparable post-tax return.
Maybe we don't need a wealth tax, but a way of unlocking capital from banks to excellent resource allocators (to be defined).