Year	% of total
1970	77.75073334419022
1971	76.97868067667183
1972	76.73000015463765
1973	76.51969567798437
1974	76.79229218884944
1975	76.83022084487463
1976	77.17800613191869
1977	76.5654123197509
1978	76.20180913225713
1979	74.60571506553893
1980	75.59438666966439
1981	76.51180979595196
1982	73.80705034167173
1983	78.29356578104914
1984	78.34983218580813
1985	77.76685628279841
1986	76.58823201437946
1987	75.72640737879517
1988	74.73052445677313
1989	74.72127548628484
1990	51.12881806108898
1991	50.26315789473684
1992	49.15032679738562
1993	45.56616643929058
1994	47.089262613195345
1995	44.59102902374671
1996	46.48275862068966
1997	47.87701317715959
1998	48.976377952755904
1999	48.59154929577465
2000	52.18978102189781
2001	52.65017667844523
2002	55.02471169686986
2003	58.76288659793815
2004	57.692307692307686
2005	58.38068181818182
2006	57.04022988505747
2007	56.87943262411348
2008	56.88456189151599