Year	Number of
1990	11.02
1991	11.46
1992	11.94
1993	12.47
1994	12.98
1995	13.57
1996	14.07
1997	14.52
1998	14.97
1999	15.48
2000	15.96
2001	16.62
2002	17.4
2003	18.16
2004	18.92
2005	19.69
2006	20.46
2007	21.14
2008	21.76
2009	22.4
2010	23.06
2011	23.64
2012	24.29
2013	24.96
2014	25.72
2015	26.53
2016	27.16