Year	Number of
1990	8.06
1991	8.45
1992	8.88
1993	9.42
1994	10.02
1995	10.67
1996	11.07
1997	11.51
1998	11.94
1999	12.37
2000	12.8
2001	13.37
2002	13.93
2003	14.57
2004	15.36
2005	16.38
2006	17.52
2007	18.96
2008	20.67
2009	22.47
2010	24.27
2011	25.94
2012	27.42
2013	28.71
2014	29.93
2015	31.18
2016	33.14