Year	Number
1975	12425
1977	14468
1978	14723
1979	16597
1980	17626
1981	18150
1983	19073
1988	25372
1989	26518
1990	27178
1991	29256
1992	30802
1993	32650
1994	34682
1999	42144
2000	42895
2001	46565
2002	48256
2003	48654
2004	48635
2005	48652
2006	48476
2007	48748
2008	50349
2009	51530