Year	Number
1976	11.28986
1977	7.71186
1980	7.75862
1981	8.01767
1985	12.32419
1986	12.42791
1987	11.68363
1988	11.82965
1989	11.75449
1990	14.34368
1992	11.73477
1993	12.03802
1994	11.54003
1995	12.23548
1996	12.82326
1997	13.1804
1998	13.33851
1999	13.61963
2001	13.12269
2002	13.1835
2003	12.04
2004	22.48668
2005	14.60693
2007	8.40785
2008	9.74747
2009	9.56519
2010	8.64295
2011	9.36098
2012	10.92094
2013	11.65756
2014	12.71012
2015	12.94287
2016	12.56286
2017	13.55156
2018	14.03418