Year	% of total
1970	2.9209292117794154
1971	2.917458823140932
1972	2.947637535167136
1973	2.9338226200807083
1974	3.066495672887427
1975	3.111600738204512
1976	3.144189427343462
1977	3.0963227723244557
1978	3.1475974298038363
1979	3.112639523457365
1980	3.049518985348442
1981	3.1424442005491002
1982	3.1064807068790214
1983	3.057579319893378
1984	3.2241141178782193
1985	3.2125585126211527
1986	3.12344937980294
1987	3.1893060846456946
1988	3.1824191438014284
1989	3.089640194168141
1990	0
1991	26.94610778443114
1992	41.86046511627907
1993	57.14285714285714
1994	63.286713286713294
1995	68.07228915662651
1996	64.45086705202311
1997	60.664819944598335
1998	58.855585831062676
1999	58.03814713896458
2000	56.60377358490566
2001	57.55813953488372
2002	56.53495440729483
2003	54.20560747663551
2004	52.41157556270096
2005	49.67105263157895
2006	52.42718446601942
2007	52.40963855421686
2008	54.09356725146199