Year	% of total
1970	36.50328240958575
1971	37.614574639566115
1972	38.101556249283554
1973	38.45510546158552
1974	38.389884769291214
1975	37.718621023643976
1976	37.8179322834952
1977	38.47303588451665
1978	37.94927601894162
1979	39.17433777843012
1980	38.810235196566566
1981	38.99680799233931
1982	39.0043768318921
1983	32.46831203258493
1984	40.797064010860936
1985	41.69429978988182
1986	40.41396894838498
1987	40.70264180516243
1988	40.163251839829556
1989	40.906902729926095
1990	35.36585365853659
1991	36.59080767514503
1992	35.957288303948346
1993	33.4496644295302
1994	33.58981162111966
1995	31.472491909385113
1996	31.285367825383993
1997	31.98985343855693
1998	32.858873410054514
1999	32.92872704637411
2000	31.04704097116844
2001	27.920962199312715
2002	28.210463733650414
2003	29.118086696562035
2004	30.438813349814588
2005	31.09217171717172
2006	32.481397605952765
2007	34.64673913043478
2008	34.494535519125684