Year	Number of
1990	251.54
1991	265.99
1992	278.88
1993	288.82
1994	297.26
1995	304.43
1996	317.3
1997	329.08
1998	338.92
1999	352.03
2000	367.48
2001	382.37
2002	395.22
2003	407.24
2004	418.89
2005	430.69
2006	439.33
2007	445.18
2008	448.97
2009	456.42
2010	463.39
2011	469.87
2012	479.54
2013	487.86
2014	493.05
2015	497.61
2016	503.31