The strong Swiss franc is causing growing concern in economic circles. Is it time for the Swiss National Bank to step in? And just how serious is the problem? Swissinfo takes a closer look. Is the strength of the Swiss franc historic? In nominal terms, the franc is currently trading near historic highs. It has never been stronger against the euro, as this chart illustrates: Against the dollar, a similar pattern emerges. One Swiss franc currently trades at $1.27, just one cent below its all-time high in August 2011. Back then, the financial crisis was raging in the US, while Europe was grappling with high debt levels. Investors lost confidence in the euro and turned to the Swiss franc. Shortly afterwards, in September 2011, the Swiss National Bank (SNB) introduced the minimum exchange rate against the euro, effectively pegging the franc to the single European currency. Times are uncertain again, albeit for different reasons, and investors are once again looking for safety. Is the …