Year	Number
1970	14003
1971	7816
1972	8873
1973	12559
1974	14908
1975	15611
1976	16726
1977	17433
1978	17732
1979	21406
1980	23355
1981	25997
1982	27799
1983	31422
1984	33564
1985	35423
1986	37343
1987	41138
1988	43695
1989	45064
1990	46303
1991	46572
1992	51895
1993	55312
1994	61615
1995	66454
1996	67454
1997	71475
1998	71262
1999	72437
2000	72992
2001	77919
2002	81128
2003	83104
2004	88142
2005	93096
2006	94545
2007	97936
2008	103317
2009	111480
2010	123307
2011	128172
2012	127852
2013	127121
2014	128473
2015	128701
2016	128780
2017	133639