Year	Number of
1990	28.54
1991	29.07
1992	29.69
1993	30.34
1994	31.15
1995	32.1
1996	32.52
1997	32.82
1998	33.41
1999	34.22
2000	35.08
2001	35.28
2002	35.5
2003	35.8
2004	36.42
2005	36.96
2006	38.27
2007	39.64
2008	41.1
2009	42.71
2010	44.45
2011	46.3
2012	48.51
2013	50.84
2014	53.33
2015	56
2016	58.74