So many ways to fail

TODAY was a brutal day for European markets that haven't had many brutal days of late. Bond yields were up around the periphery, and equities were down sharply, led lower by Italian shares. It would be premature to declare a new flare-up for the euro-area crisis. Yet this should be a reminder to Europe that complacency is the enemy and that the single currency is still in very vulnerable shape. There are simply too many ways for things to go awry.Recent economic data have been decent, by euro-area standards. While output still seems to be contracting across much of the euro area, the pace of decline seems to be easing, for industrial activity as well as employment. Given quiescent financial markets and a growing world economy, one could imagine a return to growth for the euro-area economy by the end of the year. Yet the number of potential political stumbling blocks is sufficient to...