Year	Number
1971	15025
1972	17511
1973	19182
1974	20237
1975	22287
1976	23615
1977	25266
1978	26065
1979	27031
1980	28472
1981	30078
1982	32618
1983	34805
1984	35920
1985	37967
1986	40636
1987	42502
1988	45367
1989	48097
1990	49657
1991	48650
1992	48785
1993	49059
1994	52016
1995	52130
1996	53631
1997	55636
1998	59912
1999	60989
2000	61067
2001	62465
2002	64255
2003	66473
2004	65351
2005	69991
2006	70927
2007	75451
2008	78123
2009	84645
2010	88723
2011	94985
2012	101424
2013	106801
2014	117454
2015	130464
2016	139194
2017	146418
2018	153908
2019	159109
2020	163661
2021	163290
2022	166747