Year	Number
1972	4565
1981	22102
1986	35955
1987	37937
1988	39341
1989	39154
1990	37325
1991	37653
1992	39821
1993	43034
1994	45810
1995	49008
1996	51765
1997	52499
1998	56687
1999	61711
2000	65606
2001	76658
2002	78730
2003	84407
2004	88926
2005	92796
2006	98946
2008	97213
2009	106491
2010	110206
2011	124421
2012	151531
2013	171265
2014	178968
2015	187560
2016	199920
2017	204156
2018	236775
2019	259873
2020	258338