The American Jewish population is 20 percent higher than previously reported, according to a new study released by the Brandeis University Steinhardt Social Research Institute. The institute estimated that there are 6 million to 6.4 million Jews living in the United States, along with another million people with Jewish ancestry. The estimate was based on survey data collected by a range of government, academic and private foundations. The report disputes the 2000-2001 National Jewish Population Study, which recorded a total of 5.2 million American Jews. The telephone-based survey had underestimated the number of non-Orthodox Jews and those under age 55, the new study concludes.