Year	Number of
1990	9.98
1991	10.75
1992	11.69
1993	12.82
1994	14.11
1995	15.55
1996	16.83
1997	18.16
1998	19.67
1999	21.29
2000	23.1
2001	23.8
2002	24.63
2003	25.37
2004	26.18
2005	27.03
2006	27.73
2007	28.51
2008	29.63
2009	30.98
2010	32.51
2011	33.89
2012	35.34
2013	36.81
2014	38.41
2015	40.16
2016	42.25