Year	Number
1961	11000
1962	15000
1963	18000
1964	20000
1965	22000
1966	24000
1967	25000
1968	26800
1969	40000
1970	51600
1971	53701
1972	47816
1973	53496
1974	52687
1975	54851
1976	49033
1977	64423
1978	66349
1979	70374
1980	68300
1981	65943
1982	66509
1983	66262
1984	65900
1985	68585
1986	73739
1987	74403
1988	74919
1989	76783
1990	76702
1991	76620
1992	76539
1993	76457
1994	76376
1995	76295
1996	76213
1997	76132
1998	76050
1999	75968
2000	75887
2001	75806
2002	75725
2003	75643
2004	75562
2005	75480
2006	75399
2007	72602