Year	Number
1970	8027
1971	9001
1972	10681
1973	12459
1974	14301
1975	16227
1976	17396
1977	19359
1978	20584
1979	22091
1980	23198
1981	24826
1982	26469
1983	27801
1984	28833
1985	29914
1986	30489
1987	32942
1988	35278
1989	41881
1990	41128
1991	44085
1992	51514
1993	50304
1994	52571
1995	54933
1996	57330
1998	60830
1999	61551
2000	60253
2001	60987
2002	61604
2003	61528
2004	67696
2005	70964
2006	76979
2007	82835
2009	83089
2010	88619
2011	90605
2012	91673
2013	93065
2014	96888
2015	100494
2016	104058
2017	110271