Year	Number of
1990	60.2
1991	64.59
1992	68.82
1993	72.68
1994	78.02
1995	82.68
1996	89.43
1997	98.53
1998	105.08
1999	112.81
2000	119.35
2001	123.91
2002	126.76
2003	129.13
2004	129.87
2005	131.27
2006	134.85
2007	140.9
2008	145.98
2009	150.64
2010	155.4
2011	159.9
2012	165.35
2013	174.88
2014	177.41
2015	179.74
2016	183.25