Jews are defined by those either practicing the Jewish religion who either have Jewish parentsor have converted; or else those clearly descended from Jews who identify with Jewish history and community, even if they do not practice the religion. In the United States, about 51% of the people identifying themselves as Jews actively practice Judaism. Another 43% of self-identified Jews consider themselves secular, but have Jewish parents. Of the remaining 6%, 2% have been brought up as Jews without Jewish parents and 4% are self-identified Jews without Jewish parents and without a Jewish upbringing. (Survey doesn't clear that whether 2% by upbringing believe in Judaism or not). For example according to American Jewish Identity Survey 2001 (http://www.jewishvirtuallibrary.org/jsource/US-Israel/ajis.html)
