You can’t keep a good currency down. In a desperate effort to prevent the return on its balance sheet from dipping further, Credit Suisse this week said it would charge a negative interest rate on short-term cash holdings in Swiss francs. In other words, you pay us for the privilege of storing your money. The Swissie, a safe haven in the best of times, has been straining at the leash of the Swiss National Bank over the past year as nervous companies swapped their euros for something more certain and liquid – U.S. T-bills or Swiss franc deposits.