Here is a rather balanced article on that very question.
http://www.huffingtonpost.com/jared-..._b_932625.html
Originally Posted by WTF
Sorry, but that lands well short of being classifiable as a "balanced article." The author is far-left "economist" Jared Bernstein, who in fact has multiple graduate degrees in "social work", and as far as I know has no formal training in mathematics, or even economics. He can reliably be counted on to offer the viewpoint of the very most progressive end of the political spectrum.
Be that as it may, I'll try to offer some substance and tell you just a few points I would make if I were to sit down at a table and debate this issue with Mr. Bernstein.
We have experience based on many decades during which politicians have moved the capital gains tax rate up and down. For a long period prior to the 1970s, the rate was held steady at 25%, even though the top rate on ordinary income was as high as 91%. (Although as was previously noted, hardly anyone paid tax at a rate more than a fraction of that.)
In the post-Watergate days, Democrats strengthened their hand in congress and pushed for a more liberal agenda, including increased taxes on the wealthy. But since the top rate on ordinary income was already extremely high, they concentrated on the capital gains rate, elevating it to about 39%. Analysts and financial reporters began noticing that didn't work very well, and revenues dropped substantially relative to what they had been under the 25% rate. An apparently surprised Democratic congressional majority then created and passed legislation reducing the cap gains rate to 28%, and the president signed it. You might note that it was Carter, not Reagan, who signed the legislation. Revenues increased dramatically in the years that followed, even though the equity markets sucked through the whole period (reaching new lows in 1982).
On several more occasions, revenues increased after rate cuts, and vice versa. Of course, correlation does does necessarily imply causation, and there are always multiple things going on in an economy at any given time. But I think the argument that you can push the rate to a very high level (such as 39%) without causing serious distortions is highly questionable, at best.
I also think that plotting the top cap gains rate against net real business investment misses much of the point. Initially investing is one thing. Harvesting gains in the most advantageous way with respect to all factors (including taxation) is another. When capital gains tax rates are high, investors naturally seek to lower their tax burdens. If you can match a gain with the sale of something in which you have an unrealized loss in the same tax year, you will be incentivized to try to do so. Additionally, when rates are high you may simply borrow against an appreciating asset rather than sell it. This is usually pretty easy for wealthy investors to do, and you can hedge against potential losses in a variety of ways.
You must also consider something we refer to as "lock-in effect." When capital is "locked in" to an asset or asset class by rates high enough that they reduce incentives to sell, capital may fail to flow to its highest and best use, and therefore the real economy may suffer. Reasonable people may differ on opinions of the rate threshold beyond which this becomes a potential issue, but no one familiar with the dynamics of taxation is likely to argue that it is not a factor.
Although it is very difficult to estimate the revenue-maximizing, non-distorting top tax rate on capital gains, history is clear on the fact that there is a powerful inverse correlation between the top cap gains tax rate and net capital gains realizations.