In 2012, the euro-zone countries began the process of increasing the integration of their banking systems by giving the European Central Bank the authority to supervise banks in all member countries. There was less progress on a proposal to have a single deposit insurance program for all countries. An article in the Wall Street Journal called a common deposit insurance program “a difficult political issue.” Why might the countries in the euro zone consider it necessary to have a common deposit insurance system? Why might these countries have difficulty implementing a common system?