Year	Number of
1990	60.21
1991	61.89
1992	63.52
1993	64.84
1994	65.62
1995	66.46
1996	64.83
1997	63.04
1998	60.94
1999	58.7
2000	56.86
2001	56.45
2002	57.13
2003	59.37
2004	59.42
2005	59.04
2006	59.2
2007	60.8
2008	62.14
2009	63.5
2010	65.44
2011	65.73
2012	65.59
2013	66.41
2014	67.44
2015	68.54
2016	69.17