Year	Number of
1990	10.89
1991	11.37
1992	11.76
1993	12.13
1994	12.53
1995	12.93
1996	13.37
1997	13.8
1998	14.24
1999	14.57
2000	14.92
2001	15.29
2002	15.76
2003	16.31
2004	16.88
2005	17.51
2006	18.1
2007	18.89
2008	19.71
2009	20.49
2010	21.28
2011	22.11
2012	22.96
2013	23.76
2014	24.52
2015	25.36
2016	26.16