Year	% of total
1970	58.92631372347691
1971	57.63359118067519
1972	58.216812641157766
1973	58.1575824319309
1974	56.364549803954354
1975	56.70528838482751
1976	56.54715161434156
1977	57.748283452600305
1978	54.37749775961357
1979	53.089197611735685
1980	51.36090988100689
1981	50.36173382280333
1982	47.57994384012096
1983	49.60915477734888
1984	50.98016922566472
1985	52.3121647083495
1986	53.8425177781339
1987	52.74275646112877
1988	53.22488235354405
1989	54.45728002095672
1990	63.85944700460829
1991	62.940503432494275
1992	62.2639336711193
1993	58.322771440642164
1994	57.80413561456912
1995	56.498701298701306
1996	52.483114819229236
1997	50.89574995235373
1998	50.49967311104885
1999	51.14133074307916
2000	50.50841014919699
2001	51.16838157515146
2002	51.89065625297648
2003	50.91466245705265
2004	50.87702842134885
2005	49.96316758747698
2006	48.25441947232833
2007	46.02148732583515
2008	41.3090529143966