Year	Number of
1990	26.28
1991	26.46
1992	27.16
1993	27.77
1994	28.96
1995	29.56
1996	30.22
1997	30.49
1998	30.77
1999	30.55
2000	30.89
2001	31.79
2002	32.04
2003	32.63
2004	34
2005	34.95
2006	35.58
2007	36.79
2008	38.27
2009	40.08
2010	41.81
2011	43.64
2012	45.84
2013	48.29
2014	50.79
2015	53.49
2016	56.46