Year	Number of
1990	21.13
1991	21.46
1992	21.8
1993	22.24
1994	22.72
1995	23.19
1996	23.94
1997	24.67
1998	25.49
1999	26.54
2000	27.55
2001	27.54
2002	27.46
2003	27.52
2004	27.59
2005	27.59
2006	26.75
2007	25.92
2008	25.34
2009	24.77
2010	24.29
2011	24.48
2012	24.71
2013	24.93
2014	25.23
2015	25.61
2016	25.98