Year	Number
1973	10.34132
1974	9.47166
1975	9.72618
1976	9.36609
1993	8.7207
1994	8.89643
1995	9.72966
1997	10.53314
1998	15.57477
1999	14.98969
2000	14.34758
2001	13.95371
2002	13.3118
2003	12.72636
2004	9.45999
2005	9.66166
2006	9.49064
2007	9.62452
2008	9.67692
2009	9.61574
2010	9.71082
2011	9.5108
2012	9.52382
2013	12.29939
2014	12.61897
2015	12.87345
2016	12.90017
2017	13.07043