Year	Number of
1990	10.32
1991	10.79
1992	11.37
1993	11.8
1994	12.22
1995	12.62
1996	12.98
1997	13.44
1998	13.9
1999	14.37
2000	15.02
2001	15.53
2002	16.03
2003	16.53
2004	17.03
2005	17.77
2006	18.5
2007	19.05
2008	19.7
2009	20.38
2010	21.14
2011	21.9
2012	22.7
2013	23.65
2014	24.29
2015	24.94
2016	25.58