Year	Number
1971	7.19831
1972	7.57692
1973	6.40395
1974	5.92439
1975	6.02908
1976	5.16522
1998	5.16911
1999	5.92162
2000	5.79556
2001	5.21454
2002	5.88618
2003	6.74432
2004	9.09709
2005	8.51235
2006	8.42949
2007	8.06782
2008	7.98416
2009	7.76814
2010	8.57123
2011	8.87659
2012	8.71305