Year	Number of
1990	32.9
1991	32.81
1992	33.12
1993	33.44
1994	33.92
1995	34.63
1996	35.98
1997	37
1998	39.3
1999	41.21
2000	42.85
2001	43.19
2002	43.92
2003	46
2004	48.53
2005	51.31
2006	54.84
2007	58.17
2008	61.16
2009	64.43
2010	67.34
2011	69.71
2012	73.7
2013	77.71
2014	81.96
2015	86.04
2016	89.76