Year	Number of
1990	41.59
1991	40.03
1992	37.22
1993	34.95
1994	33.86
1995	33.06
1996	33.78
1997	34.68
1998	35.7
1999	36.54
2000	37.64
2001	39.73
2002	42.24
2003	44.82
2004	47.54
2005	50.44
2006	52.31
2007	54.14
2008	55.9
2009	57.47
2010	59.4
2011	61.47
2012	63.88
2013	66.24
2014	68.77
2015	71.77
2016	75.04