Year	Number
1970	0
1971	0
1972	0
1973	0
1974	0
1975	2387
1976	2866
1977	2922
1979	2977
1980	3071
1981	2472
1982	2530
1983	2591
1984	2534
1985	2462
1986	2567
1987	2922
1988	3794
1989	4108
1990	8901
1991	12537
1992	18150
1993	48586
1994	63658
1995	80410
1996	81299
1997	78640
1998	47709
2002	55591
2009	115248
2010	79302
2011	76625
2012	70056
2013	83533.11125
2014	84565.03314
2015	78854.35143
2016	73525.8008
2017	70250.87607