Year	% of total
1970	14.645243479995163
1971	14.631147223692617
1972	15.646083750789566
1973	17.754939613844538
1974	16.593057910957036
1975	13.599744778732864
1976	12.750283999607886
1977	14.354600596421546
1978	16.145461338283884
1979	15.701598654415882
1980	16.154021964162023
1981	20.401600268000475
1982	19.359365553426663
1983	22.41679357955969
1984	22.887149841304808
1985	18.931468427652543
1986	21.22399617725675
1987	23.902262272325576
1988	22.501393455944687
1989	22.8364909351133
1990	21.122789028454243
1991	21.592295345104333
1992	22.92969001740027
1993	22.558124217875257
1994	21.292977565378997
1995	22.219987934848177
1996	23.770318767152208
1997	25.282574023992787
1998	24.94354342024225
1999	20.842614395723285
2000	20.73614508142934
2001	19.38072741761056
2002	19.47717891966262
2003	25.222248446227674
2004	22.14039591919465
2005	26.226708074534162
2006	23.601812402786233
2007	25.13291445142581
2008	28.390259083482455