Year	Number of
1990	53.39
1991	53.56
1992	51.9
1993	50.57
1994	50.65
1995	50.22
1996	50.37
1997	50.82
1998	51.63
1999	51.74
2000	52.23
2001	52.9
2002	53.97
2003	55.14
2004	56.52
2005	57.96
2006	59.17
2007	60.48
2008	62
2009	63.19
2010	64.6
2011	65.43
2012	66.49
2013	67.53
2014	68.58
2015	69.86
2016	71.19