Year	Number of
1990	46.8
1991	46.92
1992	48.31
1993	48.71
1994	51.05
1995	51.49
1996	52.59
1997	55.34
1998	57.9
1999	59.68
2000	61.25
2001	62.64
2002	65.47
2003	67.31
2004	70.09
2005	71.47
2006	72.5
2007	72.36
2008	71.38
2009	69.74
2010	68.49
2011	67.86
2012	67.39
2013	66.78
2014	65.88
2015	64.45
2016	64.03