Year	% of total
1970	59.39238356131962
1971	60.33664070777574
1972	60.34996659241172
1973	59.37638007235427
1974	58.271861265631955
1975	57.03385449518087
1976	55.11286886627539
1977	53.51327787455708
1978	52.420978287695775
1979	52.91592594505822
1980	51.9291879970835
1981	50.53156801557167
1982	49.414407323272066
1983	48.45394633092222
1984	47.42951814770351
1985	45.80042690191009
1986	44.5014899409694
1987	43.85350382578112
1988	41.14948223328733
1989	40.729874875119485
1990	19.248291571753988
1991	18.36706404214028
1992	14.920174165457183
1993	10.471567267683772
1994	12.584874736595644
1995	12.351326623970722
1996	11.657538839834581
1997	12.721819545113721
1998	13.344772967265047
1999	12.55665809138797
2000	10.281065088757396
2001	9.990824752778062
2002	9.957627118644067
2003	9.904912836767037
2004	10.95072175211548
2005	11.14979208973987
2006	10.284943517113472
2007	10.685938674910185
2008	10.920945395273025