What you see below is the American Jewish population every 5 years and the source is the American Jewish Committee archives. Where you see X indicates that they did not provide population figures for that year.
1900 …… 1,058,135
1905 …… 1,418,813
1910 …… 2,349,754
1915 …… 3,300,000
1920 ……….. x
1925 …… 3,600,800
1930 …… 4,228,029
1935 ……….. x
1940 …… 4,965,620
1945 ……….. x
1950 …… 5,000,000
1955 …… 5,200,000
1960 …… 5,367,000
1965 …… 5,612,000
1970 …… 5,870,000
1975 …… 5,800,000
1980 …… 5,860,900
1985 …… 5,705,000
1990 …… 5,700,000
1995 …… 5,650,000
2000 …… 5,700,000
2005 …… 5,280,000
2008 …… 5,275,000