Year	Number of
1990	26.65
1991	26.3
1992	26.56
1993	26.35
1994	26.25
1995	25.25
1996	26.19
1997	26.33
1998	26.66
1999	24.78
2000	24.23
2001	22.06
2002	21.8
2003	22.06
2004	22.27
2005	22.57
2006	22.41
2007	21.94
2008	22.34
2009	22.03
2010	22.49
2011	22.61
2012	22.4
2013	23.14
2014	23.45
2015	23.73
2016	23.49