Year	Number
1971	6337
1972	7416
1973	8689
1974	10494
1975	11581
1976	13621
1977	17093
1978	20732
1979	25583
1980	30630
1981	36510
1982	42967
1983	42164
1984	44650
1986	51448
1988	56573
1989	63379
1990	66371
1991	74337
1992	74944
1993	77899
1995	87041
1996	90470
1997	95530
1998	96724
1999	98362
2000	99780
2001	102145
2002	109297
2003	123930
2004	155151
2005	177033
2006	210626
2007	211490
2008	228242
2009	250143
2010	300793
2011	335784
2012	365886
2013	411568
2014	472602
2015	546679
2016	662766
2017	730124
2018	775930