Year	Number of
1990	13.29
1991	13.83
1992	14.49
1993	15.18
1994	15.92
1995	16.67
1996	17.21
1997	17.71
1998	18.18
1999	18.66
2000	19.19
2001	20.18
2002	21.31
2003	22.67
2004	24.25
2005	26.1
2006	27.31
2007	28.68
2008	30.37
2009	32.15
2010	33.99
2011	35.4
2012	36.85
2013	38.3
2014	39.75
2015	41.18
2016	42.63