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Here are yearly totals from the Mathematics Genealogy Project. (This is as of August 2012.)

Year              # of Math PhDs known to MGP
---------------------------------------------
1960                593
1961                674
1962                863
1963                1002
1964                1203
1965                1309
1966                1439
1967                1549
1968                1762
1969                1949
1970                2031
1971                1986
1972                2057
1973                1997
1974                1997
1975                1922
1976                1859
1977                1830
1978                1911
1979                1922
1980                1873
1981                1822
1982                1939
1983                2012
1984                1966
1985                2023
1986                2102
1987                2267
1988                2526
1989                2703
1990                2884
1991                3009
1992                3328
1993                3419
1994                3650
1995                3764
1996                4034
1997                4053
1998                4181
1999                4065
2000                4275
2001                3932
2002                3815
2003                3807
2004                3919
2005                4751
2006                4445
2007                4332
2008                4194
2009                3877
2010                3714
2011                3235
2012                1372
------------------------
Total 1960-2012   139143


For comparison, the total number of records in the MGP at this time is 163611.

Also, this (undated) AMS page says there are 35800 members of the four main U.S. mathematics professional societies.