Safe haven currencies

Whenever trouble brews in the global economy, some currencies tends to becaome the refuge of worried investors. There is plenty of opportunities to panic right now (rightly or wrongly), and these safe haven currencies are again being sought. So, which are they?

Angelo Ranaldo and Paul Söderlind document that these currencies vary little by circumstances. Whenever US stock markets tank, US bond prices increases or currency markets become more volatile, the euro, the British pound and especially the Swiss franc appreciate. Interestingly, such movements are visible in the data at all sorts of frequencies, including hourly data.

While I can understand why non-US currencies appreciate when there are sign of trouble in the United States, I am somewhat mystified why the Swiss franc would appreciate more that the others. While Switzerland has indeed the reputation of being a very stable country, its monetary policy follows very closely that of the Europen Central Bank (and the German Bundesbank before that). In fact, the Swiss National Bank does not like at all such appreciations, which are bad for trade in a country relying very much on its export sector. Does anybody have insights?