Year	Number
1970	3905
1971	4740
1972	5564
1973	8763
1974	10308
1975	12098
1976	13991
1977	15496
1978	16086
1979	16736
1980	18325
1981	20148
1982	20965
1983	22252
1984	27364
1985	32172
1986	35966
1987	39375
1988	40357
1989	49348
1990	56892
1991	73909
1992	75873
1993	85687
1994	86684
1995	103159
1996	109843
1998	143503
1999	148195
2000	152105
2001	151847
2002	155207
2003	156786
2004	158839
2005	160000
2006	164201
2007	168220
2008	168220
2009	171986
2012	172669
2013	174853
2014	187030
2015	169489