Year	Number of
1990	9.28
1991	9.77
1992	10.36
1993	10.92
1994	11.55
1995	12.21
1996	12.85
1997	13.42
1998	14.06
1999	14.67
2000	15.3
2001	16.98
2002	18.9
2003	21.14
2004	23.61
2005	26.34
2006	28.59
2007	31.05
2008	33.75
2009	36.62
2010	39.68
2011	42.77
2012	46.2
2013	49.96
2014	54.22
2015	59.06
2016	64.29