On the other hand: 1. Determining skill from luck is difficult if we have a very small sample of successful trades (e.g. shorting banks correctly in 2008, but

On the other hand: 1. Determining skill from luck is difficult if we have a very small sample of successful trades (e.g. shorting banks correctly in 2008, but getting everything else wrong) 2. In order for a diversified investor (e.g. into FTSE World, some bonds and precious metals) to lose everything would require one hell of a black swan. Some kind of forceful expropriation of their assets is much more likely. The problem for the shorters now is that the exact same arguments they are making now could have been made 5 years ago.