The best way to do this is to do 4 things:
1)carefully scrutinize all the ways of accessing/transferring assets and legally classify them as taxable events that cause a gain of the asset to be realized and taxed.
2)eliminate the preferential treatment of capital gains (a phase out for high incomes above half a million is the way I would do it) plus reasonable rules on spreading gains/losses to allow for reasonable adjustment of sudden spikes
3)raise marginal rates on high incomes (including both earned income as well as capital gains) with several steps along the way from our current $400K/37% marginal up to something in the 60% to 70% marginal rate for really high incomes (over $10-15 million is my threshold).
4)continue all the efforts at improving enforcement, coupled with research and response to tax avoidance/evasion techniques, updating the above laws as needed
If you do those things, you are going to capture a great deal of the gains in assets, which is the primary driving factor behind these massive increases in wealth over time.
I feel like a solid approach as I outlined will accomplish much of what liberals desire in regard to high wealth individuals.
In addition, on the more general topic of wealth inequality we also need to be looking at enforcement of rules about conflicts of interest, abuse of charity and trust rules, leveraging money for political power, better regulation on monopolies and bundling.
I’m not averse to a wealth tax but I have two areas where I think some of the current left’s focus on wealth taxes is oversold:
1)I don’t feel we’ve come anywhere close to making best use of our existing income tax system and it is riddled with loopholes and preferences for the wealthy that need to be addressed, along with a substantial increase in progressivity at the upper end.
2)I also don’t feel a wealth tax will magically solve all the problems we have with tax avoidance and tax evasion - many of the techniques used to hide or shield income from tax can be applied to wealth (manipulation and exploitation of trust rules for example, along with many others). Also there are transition costs to enacting a new system as well as frictional costs and on top of that some well known uncertainties.
I’m willing to entertain the idea of a wealth tax, but only as a modest supplement to what I’ve outlined for income taxes, and even then I don’t consider it a silver bullet.
There is no silver bullet, but we have to start with better enforcement, plugging all the loopholes to “realizing a gain”, better progressivity, and phasing out the preferential treatment of capital gains. That’s where we should focus.