Year	Number of
1990	50.88
1991	51.93
1992	52.64
1993	54.46
1994	56.15
1995	57.71
1996	59.07
1997	60.3
1998	61.34
1999	61.77
2000	62.09
2001	59.94
2002	59.13
2003	59.01
2004	59.13
2005	59.29
2006	60.07
2007	61.29
2008	63.22
2009	64.94
2010	65.96
2011	65.03
2012	64.16
2013	63.08
2014	62.18
2015	61.93
2016	62.18