Year	Number of
1990	13.96
1991	14.24
1992	14.51
1993	14.78
1994	15.08
1995	15.51
1996	15.74
1997	16.07
1998	16.34
1999	16.71
2000	17.09
2001	17.3
2002	17.62
2003	17.86
2004	18.3
2005	18.63
2006	19.28
2007	20.02
2008	20.73
2009	21.59
2010	22.46
2011	23
2012	23.74
2013	24.54
2014	25.33
2015	26.24
2016	27.17