Year	Number of
1990	242.9
1991	251.92
1992	262.37
1993	277
1994	293.24
1995	308.44
1996	319.49
1997	329.8
1998	342.97
1999	356.4
2000	370.34
2001	383.12
2002	395.67
2003	408
2004	420.67
2005	431.47
2006	439.13
2007	447.5
2008	458.9
2009	472.43
2010	489.52
2011	500.61
2012	513.47
2013	527.49
2014	543.65
2015	562.14
2016	580.93