Year	Number of
1990	32.46
1991	33.28
1992	34.16
1993	35.11
1994	36.08
1995	37.1
1996	38.44
1997	39.85
1998	41.36
1999	42.98
2000	44.72
2001	45.42
2002	46.19
2003	47.01
2004	47.88
2005	48.8
2006	48.42
2007	48.06
2008	47.79
2009	47.6
2010	47.5
2011	47.9
2012	48.4
2013	48.91
2014	49.52
2015	50.24
2016	51