Year	% of total
1970	8.411751409252123
1971	7.755299738933141
1972	7.8716337992721295
1973	7.350574765665427
1974	6.297444184159612
1975	6.285423777239912
1976	6.40211626892237
1977	6.934528746042344
1978	6.729828881457747
1979	6.94564240203365
1980	6.653648398196746
1981	6.7240012716012005
1982	7.297532589896252
1983	7.629474830513207
1984	7.340327671382807
1985	7.368106034593335
1986	7.3599342803558825
1987	7.310108234609368
1988	6.988732496099207
1989	6.834055653435107
1990	7.52539242843952
1991	7.94638583054093
1992	8.921161825726141
1993	8.664987405541561
1994	9.059912323429128
1995	9.882005899705016
1996	9.265033407572384
1997	10.031631269769543
1998	10.012782275244994
1999	10.964725881852953
2000	11.374207188160677
2001	9.837505489679403
2002	10.401785714285715
2003	10.183996576807873
2004	10.791685095090669
2005	12.030075187969924
2006	11.89488243430152
2007	12.077512392969806
2008	13.153961136023916