Year	% of total
1970	76.7673830782402
1971	76.98124522040891
1972	76.9033201162164
1973	76.86683963484879
1974	76.90966886394513
1975	77.13968501903618
1976	77.29793927969705
1977	77.51627319296254
1978	78.17218822591583
1979	78.64184397619667
1980	79.16047394040491
1981	78.95662529891257
1982	78.75817260920725
1983	78.41820687261583
1984	78.07562129455607
1985	77.69813501877523
1986	77.43715652533525
1987	77.64893401808646
1988	67.27144464395107
1989	60.13586083928555
1990	47.8108581436077
1991	47.10017574692443
1992	43.15992292870906
1993	40.33264033264034
1994	44.66403162055336
1995	43.63636363636363
1996	41.883767535070135
1997	40.31531531531532
1998	37.59213759213759
1999	35.872235872235876
2000	34.61538461538461
2001	34.065934065934066
2002	35.50135501355013
2003	35.82887700534759
2004	33.787465940054496
2005	31.932773109243694
2006	31.79190751445087
2007	30.484330484330485
2008	26.047904191616766