Year	Number of
1990	10.71
1991	11.29
1992	11.9
1993	12.51
1994	13.05
1995	13.49
1996	13.32
1997	12.98
1998	12.59
1999	12.13
2000	11.83
2001	12.09
2002	12.54
2003	13.13
2004	13.96
2005	14.84
2006	16.39
2007	17.84
2008	19.33
2009	20.79
2010	22.36
2011	23.22
2012	24.02
2013	24.67
2014	25.3
2015	25.95
2016	26.34