Year	Number
1973	34.7877
1974	38.05357
1975	37.92918
1977	38.0303
1991	29.23918
1992	29.27536
1999	19.80921
2000	19.55814
2001	18.52512
2002	18.64856
2003	19.01818
2004	19.02119
2005	18.19075
2006	17.23791
2007	17.32064
2008	16.738
2009	16.13922
2010	16.01969
2011	15.92564
2012	15.78295
2013	14.84121
2014	14.25
2015	14.00558
2016	13.07679