Year	Number
1970	27.15046
1971	25.33333
1972	25.80374
1973	26.03432
1974	25.34731
1975	27.99419
1976	25.38983
1978	25.92641
1979	24.13692
1980	24.34315
1981	24.98417
1982	21.06053
1983	19.6262
1984	20.89012
1985	22.875
1986	22.31135
1987	21.65155
1990	23.97968
1991	23.42857
1992	21.24745
1993	22.27056
1994	23.59486
1995	21.2398
1996	20.96642
1997	21.0202
1998	21.8883
1999	20.90037
2000	22.14456
2001	20.69623
2002	22.12807
2003	21.71238
2004	20.30012
2005	20.30036
2006	22.29079
2007	25.4015
2008	25.06316
2009	24.58676
2010	24.88626
2011	24.12606
2012	21.10539
2013	25.74776
2014	21.85806
2015	21.63312