Indiana, Louisiana, Maryland, New Jersey, South Carolina, Texas, Chicago and Puerto Rico with the target of delivering between 10 million and 13 million doses per month at full capacity. In May 2021, Walmart said that starting from May 18 all its fully vaccinated employees can stop wearing masks at work following the guidance from the U.S. Centers for Disease Control and Prevention. Economic impact Effects on customers A 2005 story in The Washington Post reported that "Wal-Mart's discounting on food alone boosts the welfare of American shoppers by at least per year." A study in 2005 at the Massachusetts Institute of Technology (MIT) measured the effect on consumer welfare and found that the poorest segment of the population benefits the most from the existence of discount retailers. In 2006, American newspaper columnist George Will stated that In terms of economic effects, "Wal-Mart and its effects save shoppers more than a year, dwarfing such government programs as food stamps () and the earned income tax credit ()". Effects on retailers Kenneth Stone, Professor of Economics at Iowa State University, in a paper published in Farm Foundation (1997), found that some small towns can lose almost half of their retail trade within ten years of a Walmart store opening. Presumably, people who previously shopped in towns without Wal-Mart stores choose to shop in towns with Wal-Mart stores, part of an older pattern in which smaller centers lose retail sales to larger ones. Stone compared the changes to previous competitors that small town shops have faced in the past, such as the development of the railroads, the Sears Roebuck catalog, and shopping malls. He concluded that small towns are more affected by "discount mass merchandiser stores" than larger towns and that shop owners who adapt to the ever-changing retail market can "co-exist and even thrive in this type of environment." In later research Artz and Stone (2006) reported that in MIssissippi the impact of opening a Walmart was much larger on existing retailers in rural communities (17%) than more urban ones (4%). This also suggests that Walmart has achieved its strongest growth in non-metropolitan areas, which tend to be low-income. Studies of the impact of Walmart tend to focus on Supercenters rather than Neighborhood Markets. Comparisons of performance metrics such as sales per square foot suggest that supermarkets and other high-volume retailers in direct competition with Walmart Supercenters show significant decreases in profit