Year	Number of
1990	10.61
1991	11.51
1992	12.63
1993	13.85
1994	15.15
1995	16.4
1996	17.18
1997	17.73
1998	18.13
1999	18.68
2000	19.29
2001	20.75
2002	22.46
2003	24.22
2004	25.83
2005	27.47
2006	29.28
2007	30.82
2008	33.17
2009	36.82
2010	40.62
2011	44.67
2012	50.08
2013	56.75
2014	63.81
2015	70.8
2016	76.85