Year	% of total
1970	72.17768235599198
1971	71.91464831232925
1972	70.00415719798777
1973	69.19142365857502
1974	68.26999685423715
1975	67.44907949399273
1976	65.94165559191524
1977	64.3336988814232
1978	65.46724693177512
1979	63.87062421297228
1980	64.51196369480388
1981	63.30441084761978
1982	56.08059678529699
1983	56.748203816940034
1984	54.37133445691723
1985	56.024531291120915
1986	58.36078341286727
1987	60.61684226663535
1988	58.02058520280424
1989	58.81851547633491
1990	56.67838312829525
1991	55.57537912578056
1992	54.57013574660633
1993	50.682261208576996
1994	51.52091254752852
1995	51.094196003805905
1996	51.5625
1997	52.30088495575222
1998	51.23674911660777
1999	51.58526135389888
2000	52.03657522859518
2001	51.02711585866886
2002	49.95925020374899
2003	49.64143426294821
2004	49.33852140077821
2005	48.54070660522273
2006	47.95234549516009
2007	46.52014652014652
2008	45.75908766928011