Year	% of total
1970	69.91008526529232
1971	71.05315293135105
1972	70.38535163138015
1973	69.63909673256217
1974	69.64775359756699
1975	67.46324717320498
1976	67.14781828887307
1977	64.5524972150717
1978	61.97180619694016
1979	60.98751873887353
1980	61.0755944471168
1981	60.25600086442976
1982	58.93741113029598
1983	57.64454981377494
1984	56.012416508477884
1985	54.480644124266995
1986	54.16920814644567
1987	53.677639737411596
1988	52.48087136020524
1989	52.1384073831687
1990	46.13604622504587
1991	45.9189578370813
1992	45.410158848415506
1993	44.71725011880247
1994	44.77218380404576
1995	45.87262821717077
1996	46.94608307236666
1997	44.17415027850404
1998	45.08558298416131
1999	45.280916566750236
2000	44.94762599293644
2001	43.98971086062342
2002	43.098464428155
2003	42.21911730460467
2004	42.587682294805354
2005	42.54897513340576
2006	40.165957254120634
2007	37.512478840227445
2008	35.99190616076748