Year	Number
1970	14.72238
1971	14.78571
1972	15.0523
1973	17.80402
1974	16.84319
1975	16.61163
1976	17.69022
1977	19.28448
1978	16.85346
1980	18.44239
1981	15.97912
1984	19.74569
1985	21.57851
1986	19.3722
1987	19.2956
1988	17.17606
1989	17.62651
1990	16.62191
1991	18.08859
1992	17.98925
1993	17.83202
1994	16.77845
1995	16.66177
1998	17.06238
1999	16.65829
2000	16.40179
2001	15.72677
2002	15.23473
2003	14.83252
2004	13.82745
2005	13.77713
2006	13.87902
2007	13.82065