Year	Number of
1990	18.08
1991	18.38
1992	18.73
1993	19.15
1994	19.71
1995	20.64
1996	21.06
1997	22.13
1998	23.01
1999	24.64
2000	26.23
2001	26.89
2002	27.39
2003	28.68
2004	29.24
2005	29.49
2006	29.96
2007	30.25
2008	31.08
2009	32.94
2010	32.25
2011	32.29
2012	33.04
2013	33.81
2014	34.9
2015	36.01
2016	36.9