Quote from FutsTrader111:
$2.3 trillion dollars a day exchanged. [..]
times by 0.25%:
[..]
Nearly $6 billion dollars in daily taxes
So after a 50-fold increase in price*, the quantity demanded stays the same? That is so new, man, you should publish immediately, the 'science' of microeconomics will never be the same again! Annualize this and you start being grateful that CEPR made this blunder with their measly sum of $100 billion, when they could go for as much as $1500 billion! And a simple trader's tool, the trusted MA(30) did the trick - man, they don't know a thing about trading, these economists!
But for the benefit of the tape and those working for the Robin Hood: the calculation above assumed of course that the demand curve for speculative goods is perfectly inelastic (the curve becoming in fact a vertical line). But if some market participants are less addicted to trading than intravenous drug users to heroin, then even a slightest downward slope in this demand curve will cause the quantity transacted to drop. If a good has plenty of substitutes (e.g. exchanges in other countries), demand for this good becomes very elastic indeed, and the drop will be a significant one (up to -100% for goods with perfect substitutes). Which is why only an *international* version of this tax would not marginalize US financial industry to the level of Sweden. In fact they assumed volume will decline very significantly, but perhaps not by -93% (not only a -93% fall in volume would reduce tax intake from the maximum possible 1500b to the projected 100b, because they must have made room for ample exemptions. e.g. for market making firms and banks, pension funds etc). Judging by other studies, volume would drop by 30-50%, depending on the price elasticity of demand and on whether the tax rate is tiered (computed as a proportion of the bid/ask spread for each market separately). But if done unilaterally... well, that -93% would indeed be a possiblity, especially without any exemptions for banks.
On the other hand, trying to impose an international tax would be a classic case of the prisoner's dilemma - incentives to break the ranks would be greater than in OPEC. The int. trans. tax would have to be combined with a ban on offshore market centers (including lower Earth orbit

and subordination (invasion?

of all dissident countries (such as Switzerland).
OldTrader, I think you will find that representative US stocks (by volume) are priced slightly more expensively, at around 100, not 20. Zdgreg, thanks for your suggestion, I did send my little tax 'efficiency' analysis article to Mr Calabria (entitled 'Analysis shows that everyone will bear the cost of the 0.25% stock transaction tax'

.
* i.e. a rise in the bid/ask spread (which is the real price in this market) from the current 0.01% to the post-tax level of at least 0.50% for representative stocks, i.e. ETFs priced at around $100