Year	Number of
1990	174.03
1991	183.57
1992	194.01
1993	206.32
1994	218.64
1995	231.61
1996	242.45
1997	253.88
1998	263.53
1999	275.14
2000	287.37
2001	299.61
2002	312.01
2003	325.46
2004	339.1
2005	352.35
2006	362.82
2007	372.3
2008	382.21
2009	392.85
2010	404.34
2011	416.91
2012	432.55
2013	450.68
2014	470.15
2015	491.2
2016	512.9