Year	Number
1980	25.13595
1984	22.60504
1985	22.58112
1986	22.12465
1987	29.30827
1988	28.8403
1989	22.57704
1990	22.15318
1991	19.9697
1992	20.67429
1994	18.7619
1995	18.85326
1998	19.9625
2000	19.44382
2001	18.92113
2002	16.68394
2003	17.39402
2004	17.42234
2005	17.63889
2007	16.5914
2008	16.14464
2009	14.29797
2010	14.11964
2011	13.05664
2012	15.0961
2013	14.51688
2014	13.798
2015	15.09945
2016	13.87277