Year	Number
1971	12337
1972	13000
1973	12321
1974	14624
1975	16013
1976	16671
1977	17509
1978	18534
1979	20255
1980	21198
1981	22220
1982	22287
1983	22009
1986	22546
1987	23341
1988	21986
1989	21107
1990	19697
1991	18832
1992	17668
1993	16209
1994	15065
1995	14406
1996	15012
1999	228
2001	778