Year	Number of
1990	11.68
1991	11.88
1992	12.11
1993	12.39
1994	12.7
1995	13.02
1996	13.4
1997	13.52
1998	13.6
1999	13.75
2000	13.79
2001	14.14
2002	14.54
2003	14.8
2004	15.36
2005	16.48
2006	17.49
2007	18.31
2008	20.61
2009	22.88
2010	25.06
2011	27.6
2012	29.85
2013	31.92
2014	33.96
2015	36.13
2016	38.1