Year	Number of
1990	6.29
1991	6.78
1992	7.2
1993	7.55
1994	7.82
1995	8.45
1996	9.03
1997	8.65
1998	8.59
1999	9.06
2000	9.29
2001	9.6
2002	9.67
2003	9.44
2004	9.25
2005	8.96
2006	8.7
2007	8.38
2008	7.99
2009	8.29
2010	8.77
2011	9
2012	9.2
2013	9.37
2014	9.54
2015	9.71
2016	9.83