Year	Number of
1990	25.74
1991	26.52
1992	27.26
1993	27.91
1994	28.34
1995	28.49
1996	28.12
1997	27.69
1998	27.15
1999	26.84
2000	26.7
2001	27.08
2002	28.13
2003	29.85
2004	30.07
2005	29.79
2006	30.03
2007	30.98
2008	32.19
2009	33.29
2010	34.55
2011	34.63
2012	34.63
2013	34.83
2014	35.33
2015	35.92
2016	36.26