Year	Number of
1990	11.26
1991	11.77
1992	12.28
1993	12.81
1994	13.38
1995	14.01
1996	15.09
1997	16.28
1998	17.58
1999	18.94
2000	20.37
2001	21.66
2002	22.93
2003	24.2
2004	25.51
2005	26.92
2006	27.49
2007	28.09
2008	28.75
2009	29.5
2010	30.33
2011	31.24
2012	32.26
2013	33.35
2014	34.53
2015	35.8
2016	37.12