Year	Number of
1990	10.38
1991	11.04
1992	11.71
1993	12.15
1994	12.78
1995	13.58
1996	14.59
1997	15.75
1998	16.79
1999	17.73
2000	18.61
2001	19.25
2002	19.93
2003	21.15
2004	23.16
2005	26.54
2006	29.16
2007	32.87
2008	37.24
2009	42.14
2010	46.54
2011	53.16
2012	59.34
2013	65.79
2014	72.7
2015	80.6
2016	90.12