Year	% of total
1970	42.75181596617757
1971	42.292691817022046
1972	43.30394451509065
1973	41.78219352438391
1974	41.4689725219735
1975	44.28440755536275
1976	44.51888703906325
1977	46.98195278462771
1978	49.58455492007626
1979	49.38402382013522
1980	49.311359939216246
1981	49.030104559833646
1982	52.61372607869793
1983	53.323925825904986
1984	56.14460057347394
1985	55.23502685833236
1986	55.29313975706786
1987	53.75293856314973
1988	50.430283629221705
1989	48.020737725621245
1990	54.179783140958385
1991	52.86358903158626
1992	53.6108146567058
1993	52.892561983471076
1994	53.17812269031781
1995	50.75107296137339
1996	51.32837407013815
1997	50.46594982078854
1998	49.94705259442288
1999	49.85994397759104
2000	48.422876949740036
2001	45.47094911584266
2002	48.1902058197303
2003	47.519769949676494
2004	47.03448275862069
2005	46.52578796561605
2006	56.15183246073299
2007	57.644444444444446
2008	58.67807893485497