Year	Number
1970	1042
1971	1155
1972	1303
1973	1526
1974	1625
1975	1555
1976	2244
1977	2635
1978	2984
1979	3189
1980	3547
1981	4265
1982	4594
1983	4807
1984	5118
1985	5240
1986	5336
1987	5607
1990	5636
1991	6363
1992	6666
1993	7351
1994	7811
1999	16576
2000	13527
2001	16480
2002	21700
2005	22487
2006	26345
2007	27332
2010	39706
2011	40124
2012	41660
2013	43574
2014	47050
2015	49905
2016	52673
2017	52753
2018	52566