Year	Number of
1990	7.97
1991	8.01
1992	8.01
1993	7.37
1994	8.62
1995	8.96
1996	10.57
1997	13.58
1998	15.69
1999	16.59
2000	16.33
2001	17.38
2002	16.77
2003	17.27
2004	17.33
2005	16.79
2006	17.01
2007	18.07
2008	18.96
2009	19.62
2010	21.09
2011	21.07
2012	21.89
2013	22.81
2014	23.87
2015	24.08
2016	24.52