Year	Number of
1990	25.02
1991	25.86
1992	26.79
1993	27.59
1994	28.98
1995	30.04
1996	30.24
1997	30.78
1998	31.15
1999	32.29
2000	33.82
2001	36.05
2002	38.79
2003	41.28
2004	44.28
2005	47.81
2006	49.08
2007	50.51
2008	53.14
2009	55.21
2010	56.95
2011	58.32
2012	57.92
2013	57.86
2014	59.35
2015	59.44
2016	59.69