Year	Number
1971	5476
1972	6469
1973	7041
1974	7636
1975	8703
1976	9371
1977	11198
1978	12187
1979	12987
1980	14116
1981	15342
1982	16329
1983	17155
1984	16965
1985	18106
1986	18795
1987	19270
1988	20066
1989	21112
1990	21711
1992	15062
1993	16081
1994	17424
1995	18405
1996	19097
1997	19878
1998	21307
1999	22264
2000	22244
2001	23311
2004	25290
2007	26100
2008	27496
2009	31206
2015	39804
2016	42121
2017	43838
2018	45349
2019	46114
2021	47443