Year	% of total
1970	41.89567094291588
1971	40.98350876416397
1972	43.179971772568045
1973	43.38882268570328
1974	40.23433944143633
1975	37.11408600727574
1976	33.92505288459918
1977	35.20558274142835
1978	37.74881287835639
1979	34.98069436187126
1980	32.62498233053414
1981	31.496692435871175
1982	35.97072870291134
1983	36.67715049179488
1984	42.381021420470006
1985	44.02966409599013
1986	43.54615787700637
1987	43.882025311486565
1988	44.7851203710703
1989	36.70646784072984
1990	52.56247840608085
1991	53.083201088188616
1992	54.1680216802168
1993	55.433751449351746
1994	56.46551724137932
1995	56.92140600315956
1996	57.79085215410894
1997	58.32011199253383
1998	58.0488697721241
1999	58.1233790292701
2000	58.03011879150688
2001	56.84580326623623
2002	55.142526964560865
2003	54.57391644653165
2004	53.21767784454352
2005	51.92080378250591
2006	51.853312302839115
2007	52.512057877813504
2008	53.36792942397509