Year	Number of
1990	14.68
1991	14.64
1992	14.7
1993	14.86
1994	15.25
1995	16.06
1996	16.97
1997	18.21
1998	20
1999	21.54
2000	23.23
2001	24.17
2002	24.9
2003	24.98
2004	24.31
2005	22.78
2006	21.73
2007	21.05
2008	20.53
2009	19.68
2010	19.38
2011	19.25
2012	20.02
2013	20.14
2014	20.75
2015	21.53
2016	22.48