Year	Number
1973	7.99167
1974	8.65086
1975	8.08108
1976	8.20259
1977	9.7767
1978	9.74
1979	8.72
1980	9.32841
1981	10.12109
1982	6.74055
1983	6.91816
1984	8.6411
1985	8.23056
1986	7.15925
1987	8.09113
1989	11.23547
1990	11.8822
1994	11.95973
1995	10.05253
1996	10.47269
1999	6.24558
2000	5.92397
2001	7.01019
2002	7.58961
2003	7.2737
2004	7.47995
2005	7.53567
2006	7.49762
2007	7.50058
2010	11.62077
2011	13.60424