Labor unions and activists have lobbied Congress to pass legislation to prevent the loss of America jobs to low wage countries, but measuring the actual loss of jobs has proved elusive. There is a stark absence of actual data and reliable statistics, which have hindered legislative efforts. Karen Kosanovich, an economist for the Bureau of Labor Statistics, said that even rough estimates are based on big assumptions that cannot be supported with data. Some private consulting firms have issued studies. An often-quoted study by Forrester Research Inc. predicted that 3.3 million white-collar U.S. jobs would be lost to low wage countries by 2015. However, the global consulting firm, McKinsey & Co., issued a report that suggested the U.S. economy is gaining more than it is losing from off shoring.