Year	% of total
1970	81.75484456840776
1971	81.7721304407208
1972	81.9874360843433
1973	81.71226218203462
1974	80.99448496101394
1975	81.80326861642915
1976	82.01975112585922
1977	82.42979241259565
1978	81.95501235572604
1979	82.12763575577108
1980	82.33911161744248
1981	82.54186609432782
1982	82.44042795244216
1983	82.67112107228675
1984	82.59664607738193
1985	82.39582236905288
1986	82.11003818998957
1987	81.33398515319602
1988	79.87851906065845
1989	79.60645137086516
1990	81.38271604938272
1991	81.22270742358079
1992	81.11587982832617
1993	81.25867653863952
1994	80.8983666061706
1995	80.42304230423042
1996	80.53749458170785
1997	80.49705139005897
1998	81.15884903429247
1999	80.8187134502924
2000	80.53846153846153
2001	79.93920972644378
2002	79.34782608695652
2003	79.44025834230355
2004	78.78787878787878
2005	79.54922108054359
2006	79.30116472545757
2007	78.73641304347827
2008	78.92451569806279