Year	% of total
1970	30.259604310123766
1971	31.83778546081483
1972	29.905913522982747
1973	32.135538205034095
1974	33.27098342785465
1975	33.68601800916253
1976	32.54336143828292
1977	33.18435071519383
1978	34.19572227583424
1979	36.39955099394139
1980	37.79657081400121
1981	38.753768415656104
1982	39.198166456698694
1983	41.13066540347158
1984	39.33662497893817
1985	41.41468218048581
1986	40.28374687605128
1987	40.935698510065585
1988	38.46115781814519
1989	37.740787276733265
1990	48.876722673211255
1991	46.87846324344292
1992	45.61655059401885
1993	48.80508660381495
1994	50.240219629375424
1995	49.854072698328466
1996	47.36685510264802
1997	44.71137804471138
1998	40.98060739114526
1999	41.42557651991614
2000	36.98424606151538
2001	35.61878642440864
2002	45.66026038437694
2003	38.25102233406732
2004	39.864066193853425
2005	41.98632173654475
2006	41.327800829875514
2007	38.608647450110865
2008	37.25440163306966