European stocks are a bit of a puzzle. Why do they perform so much worse than American ones? Last year was the best year for European stocks since the height of the Dotcom bubble in 1999. The STOXX Europe 600 index returned 19 per cent.  Obviously, 19 per cent in a year is good going. But it says a lot about European stocks that, in their best year since 1999, they only made 19 per cent. The S&P500 beat that in 2021, 2019, 2017, 2013, 2009 and 2003. Since 2000, the STOXX has returned an average of 4.5 per cent.…