Year	Number of
1990	71.26
1991	69.68
1992	68.06
1993	66.57
1994	65.04
1995	63.5
1996	64.03
1997	64.38
1998	64.75
1999	65.75
2000	66.92
2001	67.27
2002	67.83
2003	68.53
2004	69.44
2005	70.57
2006	72.73
2007	74.97
2008	77.54
2009	80.3
2010	83.42
2011	85.46
2012	87.8
2013	89.93
2014	92.35
2015	95.04
2016	97.97