Year	Number
1971	24881
1972	25498
1973	25809
1974	25913
1975	25593
1976	25032
1977	24878
1978	23206
1979	23795
1981	21999
1982	23225
1983	24216
1984	24521
1985	24090
1986	23618
1987	22742
1988	21539
1989	23385
1990	23145
1991	23630
1992	24307
1993	27502
1994	27420
1995	26689
1996	28356
1998	37498
1999	35786
2000	38196
2001	35611
2002	34795
2003	33737
2004	32558
2005	30952
2006	30226
2007	24713
2008	24893
2009	24890
2010	24769
2011	24880
2012	25161
2013	25979