Year	Number
1972	22.69642
1973	23.56192
1974	23.14583
1979	23.58637
1984	21.10154
1987	20.00557
1992	20.16941
1993	20.35371
1994	22.61182
2007	15.67164
2008	16.57498
2009	16.01028
2010	15.96033
2011	15.21755
2012	15.33509
2013	14.20295
2014	14.59321
2015	14.24161