Entirely too frenetic?

INVESTORS, like teenagers, are happiest chasing fashion. In the 1990s, indexed mutual funds became a must-have investment. Now the coolest things on the planet seem to be exchange-traded funds (ETFs)—baskets of securities that can be traded throughout the day, chiefly on the American Stock Exchange or, in Europe, on the Frankfurt stockmarket. Assets in these grew by 16.2% in the first half of this year, according to Morgan Stanley. So popular have they proved in Frankfurt, says Deutsche Börse, which runs the exchange, that the spread between the buying and selling prices of ETFs tracking the DAX index was squashed by more than half last year.