Year	Number of
1990	12.18
1991	12.55
1992	13.03
1993	13.55
1994	14.14
1995	14.78
1996	15.21
1997	15.65
1998	16.12
1999	16.63
2000	17.22
2001	17.87
2002	18.62
2003	19.5
2004	20.39
2005	21.26
2006	21.95
2007	22.59
2008	23.36
2009	24.15
2010	24.98
2011	25.13
2012	25.34
2013	25.54
2014	25.77
2015	26.06
2016	26.46