Year	Number of
1990	12.24
1991	12.63
1992	12.9
1993	13.2
1994	13.51
1995	13.83
1996	13.94
1997	14.01
1998	13.93
1999	14.27
2000	14.33
2001	14.59
2002	14.82
2003	15.06
2004	15.37
2005	15.48
2006	15.39
2007	15.41
2008	15.41
2009	15.45
2010	15.58
2011	15.74
2012	15.8
2013	15.86
2014	15.94
2015	16.05
2016	16.22