Year	Number of
1990	12.32
1991	12.9
1992	13.4
1993	13.91
1994	14.19
1995	14.35
1996	14.74
1997	15.24
1998	15.87
1999	17.19
2000	18.29
2001	19.6
2002	20.72
2003	22.07
2004	23.06
2005	24.2
2006	25.55
2007	27.07
2008	28.79
2009	30.49
2010	32.12
2011	33.6
2012	34.86
2013	36.4
2014	37.33
2015	38.19
2016	39.21