The chemical spill in the Elk River, which contaminated the water supply of 300,000 people, cost the West Virginia economy just over $19 million a day for each business day the “do not use” order was in effect, according to Marshall University researchers.The estimate by the Center for Business and Economic Research at Marshall said the estimate does not include any multiplier effects. The $19 million per business day amounted to about 24 percent of the economic activity of the region affected by the spill, which was composed of parts of nine counties.Over the four days immediately following the ban — two business days and two weekend days — the impact was about $61 million, the researchers said. About 75,000 workers were affected each day the ban was in effect. That was about 41 percent of the area’s work force, and lower-wage, service-producing workers were affected more than those in higher-wage industries. The estimated $61 million of lost output does not include the cost of cleaning up the spill or any emergency expenditures made, so it does not represent the full impact of the spill, a statement from the CBER said.