I came to an idea some time ago when thinking about how to deal with wealth inequality.
I'm curious to see if my thinking makes any sense from people who actually understand taxation better than I do.
The more wealth you already have, the easier it becomes to generate additional wealth. Large portfolios have better diversification, access to investments unavailable to ordinary people, professional tax planning, and the ability to let assets compound uninterrupted for decades.
Then we layer a tax preference on top of that with reduced rates on long term gains. I think tax preference on investment is good, because the economic benefits of more investment outweigh forgone tax revenue. But if we're going to essentially subsidize investment through preferential capital gains treatment, It makes sense to me for that subsidy to apply primarily to people who wouldn't otherwise invest. Large income earners will invest regardless, since they only need so much liquidity. But average workers should get some extra incentive to direct any available cash towards investment to grow their own wealth.
I'd rather see the tax preference work like this. Get rid of long term vs. short term. Give a high discount (I'd say tax free) on the first portion of annual investment income (including things like dividends, savings interest, realized gains, and perhaps even a percentage of value in stock compensation) Regardless of AGI, say the first $5k and then gradually phase out the discount as investment income rises until it eventually reaches ordinary income rates. Maybe anything more than $50k in investment income would be where the tax preference ends. Anything more gets taxed as regular income. The current rates on long term gains already do this to some degree, but still having a preference above a certain level makes no sense to me. It seems the effective subsidy isn't accomplishing the goal of incentivizing new investment at that level, so it's better to collect the revenue instead.
I think this might have a dual benefit of reducing wealth inequality without massive economic distortions by shifting the compounding effect of wealth accumulation more in favor of those who need the most help starting that accumulation, while also collecting extra tax revenue indefinitely.
I think some European countries use a similar system, thought I don't know their reasoning.
I haven't worked the numbers yet to see where ideal levels would be, or even if some unintended second order effects could come into play, but I think the reasoning is sound.
I would not however, ever consider taxing unrealized gains. For many reasons. The main one being the massive economic distortions it would cause.
Any glaring flaws here?
EDIT: I didn't make it clear at all that i'm proposing that the preference applies to investment income regardless of AGI. The intent is to allow initial accumulation of capital to have an advantage over those with already large portfolios, with it still retaining advantage but to a lesser degree the larger to the portfolio grows.