Year	Number of
1990	63.41
1991	61.56
1992	61.15
1993	60.26
1994	60.8
1995	59.5
1996	58.39
1997	56.43
1998	54.88
1999	52.81
2000	52.52
2001	53.74
2002	53.55
2003	54.08
2004	56.06
2005	57.02
2006	56.96
2007	58.04
2008	59.65
2009	61.83
2010	63.51
2011	65.46
2012	67.91
2013	70.66
2014	73.13
2015	75.85
2016	79.27