Year	Number of
1990	12.75
1991	12.93
1992	13.05
1993	13.31
1994	13.64
1995	14.11
1996	14.29
1997	14.55
1998	14.75
1999	14.93
2000	15.15
2001	15.04
2002	15.25
2003	15.56
2004	16.02
2005	16.64
2006	17.23
2007	17.99
2008	19.15
2009	20.24
2010	21.25
2011	21.88
2012	22.19
2013	22.55
2014	22.77
2015	23.27
2016	24.22