Year	Number of
1990	46.9
1991	48.68
1992	50.55
1993	52.81
1994	55.26
1995	57.97
1996	59.82
1997	61.47
1998	63.32
1999	65.51
2000	67.85
2001	68.2
2002	68.68
2003	69.44
2004	70.45
2005	71.73
2006	73.62
2007	75.56
2008	77.81
2009	80.05
2010	82.74
2011	84.88
2012	87.09
2013	89.44
2014	91.9
2015	94.57
2016	97.07