Year	Number
1970	1292
1971	1470
1972	1631
1973	1866
1974	1937
1975	2188
1976	2284
1977	2400
1978	2891
1979	2802
1980	2644
1981	2814
1983	2758
1984	3538
1985	3972
1986	3747
1987	3577
1988	3837
1989	4501
1990	4875
1991	4089
1992	4485
1993	4971
1994	5178
1995	7975
1998	9939
1999	9609
2000	10896
2001	11507
2002	10882
2003	11133
2004	12649
2005	13027
2006	12701
2007	10094