Year	Number of
1990	9.35
1991	10.27
1992	11.14
1993	11.83
1994	12.64
1995	13.47
1996	14.2
1997	14.93
1998	15.35
1999	15.15
2000	15.51
2001	16.58
2002	17.2
2003	17.48
2004	17.81
2005	18.58
2006	19.74
2007	21.13
2008	22.58
2009	24.18
2010	25.59
2011	27
2012	28.3
2013	29.73
2014	31.61
2015	32.71
2016	34.62