Year	Number of
1990	32.01
1991	33.22
1992	32.87
1993	33.77
1994	34.78
1995	34.59
1996	34.63
1997	34.98
1998	35.46
1999	36.24
2000	37.84
2001	40.08
2002	42.14
2003	43.83
2004	47.43
2005	49.77
2006	50.65
2007	54.14
2008	56.76
2009	60.2
2010	62.39
2011	62.83
2012	63.49
2013	65.34
2014	65.62
2015	66.65
2016	68.23