The Kingdom\'s stock exchange made its largest one-day drop in three weeks yesterday as global market jitters and volatile oil prices spurred investors to reduce their risk exposure.   The Tadawul All-Share Index (TASI) dropped 2 percent to close at 7,221.5 points, its biggest one-day loss since April 15. The market is still up 12.52 percent so far this year. The TASI fell along with stock markets around the world owing to heightening concern about the prospects for the euro zone, said Paul Gamble, chief economist and head of research at Jadwa Investment. Saudi Basic Industries Corp. (SABIC) and Al-Rajhi Bank fell 1 percent each. The insurance stocks were the worst hit yesterday as the index dropped 5.2 percent. The value of traded shares reached SR7.87 billion. \"The ongoing failure of Greek political parties to form a new government has raised prospects of a new election and brought closer the possibility of a Greek exit from the euro zone,\" Gamble added. Jarmo T. Kotilaine, chief economist at the National Commercial Bank, said: \"The swing of the European political mood away from austerity, as reflected by the anti-incumbent vote in France and Greece, has clearly intensified market perceptions of uncertainty and risk. In particular, the political stalemate in Greece and the growing frustration of especially with this, is beginning to raise existential questions about the euro zone.\" He said the possibility of a Greek exit from the euro was being openly discussed in Greece and outside. Such a possibility in turn is heightening speculation about contagion, potentially even into major economies such as Spain and Italy, said Kotilaine. \"Should the euro zone indeed unravel, even just partially, the market disruptions would be potentially enormous even though important preventive steps have been taken to contain potential damage,\" he said. Basil Al-Ghalayini, CEO of BMG Financial Group, commented: \"With the market concern at Greek instability, the Spanish government\'s bail out of the third largest bank and the unknown outcome of the newly elected French leadership, the euro zone is in crisis. Considering the correlation of the Saudi market with those of major market zones, this decline is expected.\" Farouk Miah, head of equity research at NCB Capital, said: \"I think its a combination of heightened worries in Europe due to the outcome of the French and Greek elections. Investors are selling out before the summer lull, as well as profit-taking from the very good Q1, 2012 performance.\" He added: \"It is not surprising that speculative names are falling the most, given the lack of any fundamental story in many of those names. We continue to prefer quality names which are locally driven and defensive such as Savola and Mobily.\"