Year	Number of
1990	53.8
1991	48.96
1992	45.75
1993	46.25
1994	46.22
1995	49.88
1996	51.37
1997	52.73
1998	52.37
1999	51.64
2000	52.53
2001	51.62
2002	52.21
2003	55.41
2004	59.24
2005	62.09
2006	65.16
2007	66.27
2008	66.78
2009	66.59
2010	68.05
2011	68.66
2012	72.5
2013	74.84
2014	78.79
2015	81.52
2016	87.4