Year	Number of
1990	5.17
1991	5.63
1992	6.05
1993	6.42
1994	6.75
1995	7.03
1996	7.82
1997	8.78
1998	9.93
1999	11.25
2000	12.76
2001	13.21
2002	13.78
2003	14.85
2004	16.99
2005	20.72
2006	23.11
2007	27.03
2008	31.91
2009	37.11
2010	42.27
2011	48.58
2012	54.22
2013	59.16
2014	63.27
2015	66.71
2016	74.08