Some proposals for a "wealth tax" include a mechanism called Mark-to-market. This is not foreign to accounting as some international standards employ this approach with revaluation of assets.

From a tax perspective, the idea is to revalue all investments to market value and pay tax on any appreciation (capital gains), whether the asset was sold or not during the tax year. What do you think of this idea? Do you think it is feasible and would raise tax revenues? What do you think are some potential unintended consequences associated with this approach?