Year	Number of
1990	10.15
1991	10.41
1992	10.67
1993	10.96
1994	11.27
1995	11.64
1996	12.13
1997	12.69
1998	13.26
1999	13.96
2000	14.64
2001	14.71
2002	14.7
2003	15.03
2004	15.25
2005	15.43
2006	15.67
2007	15.75
2008	16.13
2009	16.7
2010	16.87
2011	17.21
2012	17.63
2013	18.08
2014	18.64
2015	19.23
2016	19.79