A 2001 McKinsey Global Institute study of U.S. labor productivity growth between 1995 and 2000 concluded that "Wal-Mart directly and indirectly caused the bulk of the productivity acceleration" in the retail sector.[132] Robert Solow, a Nobel laureate in economics and an adviser to the study, stated that "[b]y far the most important factor in that [growth] is Wal-Mart."[133] The Economic Policy Institute estimates that between 2001 and 2006, Wal-Mart's trade deficit with China alone eliminated nearly 200,000 U.S. jobs.[134] Another study at the University of Missouri found that a new store increases net retail employment in the county by 100 jobs in the short term, half of which disappear over five years as other retail establishments close.[135] A 2004 paper by two professors at Pennsylvania State University found that U.S. counties with Walmart stores suffered increased poverty compared with counties without Wal-Marts.[136] They hypothesized that this could be due to the displacement of workers from higher-paid jobs in the retailers customers no longer choose to patronize, Wal-Mart providing less local charity than the replaced businesses, or a shrinking pool of local leadership and reduced social capital due to a reduced number of local independent businesses.[136] Dr Raj Patel, author of "Stuffed and Starved: Markets, Power and the Hidden Battle for the World Food System", said in a lecture at the University of Melbourne on September 18, 2007, that a study in Nebraska looked at two different Wal-Marts, the first of which had just arrived and "was in the process of driving everyone else out of business but, to do that, they cut their prices to the bone, very, very low prices".