Year	Number of
1990	12.95
1991	13.08
1992	13.16
1993	13.24
1994	13.31
1995	13.42
1996	14.31
1997	15.29
1998	16.35
1999	17.47
2000	18.63
2001	19.89
2002	21.16
2003	22.48
2004	23.9
2005	25.48
2006	25.24
2007	25.07
2008	24.98
2009	24.92
2010	24.9
2011	25.03
2012	25.2
2013	25.35
2014	25.51
2015	25.66
2016	25.91