Year	Number of
1990	12.77
1991	12.77
1992	12.81
1993	13.02
1994	13.32
1995	13.72
1996	13.92
1997	14.19
1998	14.43
1999	14.58
2000	14.86
2001	14.79
2002	14.98
2003	15.22
2004	15.63
2005	16.28
2006	16.99
2007	17.96
2008	19.24
2009	20.46
2010	21.61
2011	22.31
2012	22.69
2013	23.17
2014	23.47
2015	23.99
2016	24.99