Year	Number of
1990	53.24
1991	54.86
1992	55.99
1993	59.27
1994	61.91
1995	61.26
1996	61.85
1997	61.43
1998	63.17
1999	65.14
2000	68.31
2001	66.96
2002	68.14
2003	68.18
2004	68.34
2005	68.41
2006	68.97
2007	68.8
2008	67.52
2009	66.46
2010	66.36
2011	68.12
2012	69.41
2013	71.38
2014	71.73
2015	72.1
2016	73.29