Year	Number of
1990	7.86
1991	8.17
1992	8.52
1993	8.88
1994	9.26
1995	9.65
1996	9.7
1997	9.72
1998	9.75
1999	9.78
2000	9.83
2001	10.33
2002	10.87
2003	11.46
2004	12.07
2005	12.71
2006	13.58
2007	14.51
2008	15.49
2009	16.52
2010	17.6
2011	19.08
2012	20.66
2013	22.35
2014	24.19
2015	26.21
2016	28.33