Year	Number of
1990	41.7
1991	43.09
1992	44.71
1993	46.41
1994	47.89
1995	49.42
1996	50.67
1997	52
1998	53.27
1999	54.55
2000	55.44
2001	57.32
2002	58.54
2003	58.57
2004	59.74
2005	62.24
2006	62.36
2007	64.34
2008	66.62
2009	68.16
2010	71.12
2011	71.47
2012	72.96
2013	73.97
2014	75.66
2015	79.01
2016	81.64