Year	Number of
1990	55.61
1991	56.07
1992	55.96
1993	55.54
1994	56.49
1995	57.19
1996	57.5
1997	58.06
1998	58.93
1999	59.84
2000	60.54
2001	61.61
2002	62.4
2003	64.77
2004	66.43
2005	67.29
2006	68.6
2007	69.22
2008	70.29
2009	72.11
2010	75.15
2011	79.24
2012	81.11
2013	82.58
2014	84.79
2015	87.27
2016	89.83