Year	Number of
1990	7.85
1991	8.29
1992	8.8
1993	9.39
1994	10.05
1995	10.78
1996	11.75
1997	12.84
1998	14.07
1999	15.47
2000	17.08
2001	17.89
2002	18.79
2003	19.77
2004	20.81
2005	21.9
2006	22.46
2007	22.98
2008	23.5
2009	24.05
2010	24.65
2011	25.77
2012	27.01
2013	28.29
2014	29.62
2015	30.97
2016	32.36