Year	Number of
1990	59.35
1991	57.97
1992	53.97
1993	50.42
1994	48.58
1995	46.91
1996	46.32
1997	45.93
1998	45.92
1999	45.91
2000	46.31
2001	47.16
2002	48.2
2003	49.53
2004	51.02
2005	52.5
2006	53.91
2007	55.22
2008	56.68
2009	57.98
2010	59.19
2011	60.53
2012	61.69
2013	62.83
2014	63.95
2015	65.11
2016	66.66