It is the biggest monetary policy experiment of modern times. One that has divided economists, central bankers and politicians. But now that Sweden has called a halt to its five-year trial with negative interest rates the serious work has begun on looking at whether it worked. 

Sweden’s Riksbank, the world’s oldest central bank, was the  first to take its main repurchase rate — at which commercial banks can both borrow or deposit money — negative in early 2015, to fend off deflation, only returning to zero in December. 

The  end of the Swedish experiment is being watched with intense fascination, not just by those central banks that still have negative rates such as the European Central Bank and Bank of Japan, but also by authorities and economists worldwide pondering how to respond to the next downturn with limited ammunition to stimulate the economy.