Year	Number
1971	55.38453
1972	55.71323
1973	54.77386
1974	52.9007
1975	51.56871
1976	50.81095
1983	46.3499
1985	43.44283
1998	30.66259
1999	31.18106
2000	31.03273
2002	32.60835
2004	25.23843
2005	24.32793
2006	22.51085
2007	23.88067
2008	19.62249
2009	25.18972
2010	25.53138
2011	25.45855
2012	23.6279
2013	23.49304
2014	20.56358
2015	18.29098
2016	18.52102
2017	18.91694
2018	18.92322