Year	% of total
1970	55.11720497341024
1971	55.59897428473006
1972	54.99307571021289
1973	53.80368404509912
1974	52.70320510436187
1975	51.68871419500991
1976	50.00395819660527
1977	48.51721576486992
1978	47.52239984052185
1979	46.35735951978972
1980	45.28902708809009
1981	44.031267309824116
1982	42.91235740633789
1983	41.839884400712485
1984	41.159742013418494
1985	40.02809403433182
1986	39.0031331212116
1987	38.25347957616644
1988	37.1869523143317
1989	37.22900960130439
1990	19.402074435631484
1991	19.696969696969695
1992	17.86918408631153
1993	17.717086834733895
1994	17.246376811594203
1995	17.77777777777778
1996	17.248603351955307
1997	17.159763313609467
1998	16.91542288557214
1999	16.706021251475796
2000	16.42294713160855
2001	16.041666666666668
2002	15.418287937743191
2003	15.072859744990893
2004	14.622641509433961
2005	14.187271990271585
2006	12.15046604527297
2007	10.529295216529862
2008	9.375