Year	Number of
1990	48.02
1991	49.15
1992	50.41
1993	51.95
1994	53.34
1995	54.88
1996	55.89
1997	57.9
1998	59.77
1999	61.83
2000	64.1
2001	65.1
2002	66.33
2003	67.42
2004	68.42
2005	69.11
2006	69.5
2007	71.4
2008	72.45
2009	72.97
2010	73.51
2011	76.23
2012	77.27
2013	78.94
2014	81.28
2015	84.04
2016	87.18