Year	Number of
1990	321.55
1991	325.94
1992	327.39
1993	326.61
1994	326.53
1995	326.65
1996	323.17
1997	323.73
1998	330.94
1999	338.97
2000	353.25
2001	373.41
2002	400.46
2003	432.15
2004	459.83
2005	483.41
2006	501.92
2007	514.85
2008	523.07
2009	530.4
2010	539.75
2011	545.34
2012	552.62
2013	566.71
2014	588.95
2015	585.83
2016	580.41