Year	Number of
1990	10.96
1991	11.41
1992	11.74
1993	12.03
1994	12.36
1995	12.71
1996	12.84
1997	12.99
1998	13.04
1999	13.42
2000	13.6
2001	13.86
2002	14.04
2003	14.17
2004	14.38
2005	14.53
2006	14.52
2007	14.59
2008	14.67
2009	14.78
2010	14.97
2011	15.18
2012	15.29
2013	15.41
2014	15.56
2015	15.73
2016	15.96