Year	Number of
1990	35.59
1991	37.48
1992	39.53
1993	41.62
1994	43.7
1995	45.77
1996	45.91
1997	45.95
1998	46.08
1999	46.42
2000	47.03
2001	47.82
2002	48.84
2003	50.08
2004	51.46
2005	52.95
2006	54.57
2007	56.25
2008	58.22
2009	60.35
2010	62.68
2011	64.31
2012	66.12
2013	68.24
2014	70.52
2015	72.93
2016	75.37