May 24th 2010 | From The Economist onlineTHE clearest measure of recent investor uncertainty is the VIX or volatility index, traded on the Chicago Board Options Exchange. The index shows the price investors are willing to pay to insure themselves against substantial market moves. Having declined pretty steadily since the middle of 2009, the VIX has more than doubled in May and hit its highest level for over a year last week as it became clear that the euro-zone's rescue package on May 10th had not steadied government-bond markets as much as was hoped. Another concern for investors is fiscal policy. While they want governments to cut their deficits, they also worry about the impact of many developed countries doing so at once.