Year	Number of
1990	7.15
1991	7.49
1992	7.87
1993	8.25
1994	8.65
1995	9.06
1996	9.48
1997	9.92
1998	10.37
1999	10.84
2000	11.38
2001	12.03
2002	12.77
2003	13.6
2004	14.49
2005	15.45
2006	16.34
2007	17.25
2008	18.24
2009	19.3
2010	20.48
2011	21.46
2012	22.56
2013	23.78
2014	25.03
2015	26.32
2016	27.73