Yesterday, European regulators extended the ban on short selling financial stocks in four countries: France, Italy, Spain, and Belgium. The ban was started on August 12 despite any highly unusual shorting activity up until that time. The ban was originally slated to run for 15 days, expiring today. The extension will run until 11/11/11 for France and September 30 for the other countries, barring any further extensions. While these actions will not stop the slide of European financials, they will highlight the incompetence of European financial regulators. The supposed leaders of the financial markets have thrown up their hands in dismay and cried “Uncle!” almost ensuring that markets will tank by undermining investor confidence. One does not often see a government signal to the world that it has no idea what to do about its economy. It is almost as if their plan is to place a “Please, don’t kick me.” sign on the back of their weakest members.
The Theory: Mechanics & Risks

The short sale bans do not work (the top chart shows the US ban from 8/08) mainly because the underlying company fundamentals (i.e. the value of the company) do not change, but also because today’s breadth of interconnected financial products makes it almost trivially easy to develop synthetic short positions. To create such a synthetic short one would look to build an arbitrage position but simply leave a hole where the banned security would otherwise fit in the portfolio. For example the most direct way to build a synthetic short here would be to short a European financials ETF and then use the proceeds to buy up the individual components, say German, Danish, and maybe Polish financials but not those from France, Italy, Spain or Belgium. The net effect is that one has a short exposure to securities that one is not technically allowed to short. The hitch is that everyone knows this and the European financials ETF becomes hard to borrow, driving up the costs.