The difference is that individual investors will often hold on to their shares for months or years, rendering the trading tax insignificant. The tax is targeti

The difference is that individual investors will often hold on to their shares for months or years, rendering the trading tax insignificant. The tax is targeting (very) short-term professional traders, selling and buying back shares multiple times a day (or per second, in some cases). This type of trading adds little value to the useful allocation of capital, and imposes a 'tax' on other traders. To me, that sounds like as good a thing to tax as any. Besides, I'd guess that implementation of such a tax would be relatively straightforward, as far as taxes go.