Year	Number of
1990	14.83
1991	14.7
1992	14.63
1993	14.61
1994	14.68
1995	14.83
1996	15.05
1997	14.97
1998	15.17
1999	15.42
2000	15.81
2001	15.75
2002	15.73
2003	16.06
2004	16.39
2005	16.86
2006	17.36
2007	17.97
2008	18.64
2009	19.39
2010	20.18
2011	21.01
2012	21.8
2013	22.73
2014	23.87
2015	25.17
2016	26.45