Year	Number of
1990	43.44
1991	44.08
1992	44.84
1993	45.47
1994	46.21
1995	46.87
1996	46.95
1997	46.53
1998	46.28
1999	45.5
2000	45.08
2001	44.86
2002	45.26
2003	46.17
2004	47.6
2005	49.03
2006	50.67
2007	52.19
2008	53.94
2009	55.79
2010	58.29
2011	61.23
2012	64.14
2013	66.92
2014	70.07
2015	73.15
2016	76.39