Year	Number of
1990	22.31
1991	22.63
1992	22.94
1993	23.48
1994	24.14
1995	24.77
1996	25.29
1997	25.74
1998	26.11
1999	26.42
2000	25.98
2001	27.47
2002	27.04
2003	26.83
2004	26.82
2005	26.51
2006	26.25
2007	25.42
2008	24.68
2009	24.16
2010	24.22
2011	24.32
2012	24.46
2013	24.44
2014	24.32
2015	24.17
2016	24.11