Year	Number of
1990	5.58
1991	5.9
1992	6.25
1993	6.62
1994	7.01
1995	7.44
1996	7.56
1997	7.61
1998	7.7
1999	7.75
2000	7.87
2001	8
2002	8.13
2003	8.3
2004	8.47
2005	8.69
2006	8.6
2007	8.57
2008	8.61
2009	8.7
2010	8.8
2011	8.71
2012	8.67
2013	8.72
2014	8.85
2015	9
2016	9.18