Investors Are Lab Rabbits in Central Bank Experiments

The European Central Bank and Bank of England are emulating Ben S. Bernanke’s experiment in offering monetary-policy guidance to financial markets. Investors could well end up being the guinea pigs.

Bond prices have fluctuated during the last three months, with the yield on the 10-year Treasury note swinging from 1.63 percent to 2.74 percent, the fastest jump since 2010, as the Federal Reserve chairman struggled to provide a clearer picture of when and why the central bank will reduce and then end its asset purchases.