By Andrew Seidman WASHINGTON--A business research group launched a global food security index Tuesday that will monitor closely the affordability, accessibility and quality of food in nations around the world, identifying potential crises in real time. The group, the Economist Intelligence Unit, will adjust its rankings of 105 nations every quarter after taking into account changes in global commodities prices in an effort to keep the index "relevant" and to "keep it moving," Leo Abruzzese, director of Americas and Global Forecasting for the EIU, said Tuesday at the National Press Club. "We're going to have a rolling price adjustment because at the end of the day there is nothing that can shock the food security system more than having a drought or having a crop failure in a country that pushes global commodities prices up sharply," Mr. Abruzzese said. Countries in sub-Saharan Africa and South Asia are most vulnerable to price shocks because food consumption for people in those regions frequently accounts for about 50% of household spending, according to an EIU report published Tuesday. In 2008, such price volatility sent 44 million people below the poverty line, according to the World Bank. The index defines food security as "when people at all times have physical, social and economic access to sufficient and nutritious food that meets their dietary needs for a healthy and active life." The average person needs 2,300 calories per day to be healthy, according to the Food and Agriculture Organization. But the vast disparity in food supply means that people in wealthy nations eat 1,200 calories more per day than people in low-income nations. The index selected 105 nations based on regional diversity, economic importance and population size. The five most food-secure nations were the United States, Denmark, Norway, France and the Netherlands. The least food-secure countries were the Democratic Republic of the Congo, Chad, Burundi, Haiti and Madagascar. The index will "help us create a common language and give us a common data set that then we can then analyze and get into the real discussions around what's driving [food insecurity] in a specific country and hence what could be helpful to improving it," said Ellen Kullman, chief executive of the chemicals giant E.I. DuPont de Nemours & Co. (DD), which commissioned the study.