Year	% of total
1970	64.04918900856933
1971	63.275226814229754
1972	63.03390676488551
1973	60.98669430095271
1974	59.904911447367894
1975	58.298256063048356
1976	57.692002091244866
1977	56.61889662963936
1978	56.241256642501
1979	55.244574837587315
1980	53.63344915033156
1981	51.743563163837734
1982	51.35952977308178
1983	52.52797864051081
1984	51.653193049499826
1985	51.03531301067898
1986	49.03639050273358
1987	47.68164987376254
1988	46.24278419630426
1989	47.385511617050916
1990	33.390469660610215
1991	33.667820069204154
1992	34.78414720452937
1993	36.36690647482014
1994	36.51482284887925
1995	37.003281079110465
1996	37.165298107818636
1997	36.440677966101696
1998	37.377911344853494
1999	35.86545729402872
2000	34.54407869844873
2001	33.44469190794358
2002	32.76690062800148
2003	32.20338983050847
2004	33.61216730038023
2005	33.64875094625284
2006	34.01360544217687
2007	35.10313216195569
2008	35.61329766908674