Year	% of total
1970	86.75800658826194
1971	86.83170478548627
1972	86.97663392415784
1973	87.87740108877071
1974	87.73766201389579
1975	87.8678393864552
1976	87.74024858327786
1977	87.71497778203087
1978	87.80099490985921
1979	88.05378096548799
1980	87.87474812900557
1981	88.26921596575914
1982	88.07443048197307
1983	88.11263072291389
1984	87.38891493398806
1985	86.44310515941052
1986	86.23000869225842
1987	85.7332183452376
1988	85.15806698702409
1989	84.96164693898365
1990	79.02097902097903
1991	77.77777777777779
1992	76.44341801385681
1993	75.17084282460137
1994	71.98067632850241
1995	68.31168831168831
1996	66.23376623376623
1997	63.84615384615384
1998	62.03473945409429
1999	58.95522388059702
2000	56.43564356435643
2001	55.0251256281407
2002	53.316326530612244
2003	51.67958656330749
2004	50.13123359580053
2005	50.76142131979695
2006	49.48979591836735
2007	51.08958837772397
2008	52.093023255813954