Year	% of total
1970	8.641743787626151
1971	7.485271128759749
1972	7.332885401773321
1973	7.466466762345856
1974	7.81629498863925
1975	8.096681085731364
1976	7.9732557911458946
1977	8.625773635004775
1978	9.411204558077703
1979	9.77724607396838
1980	8.829265445809298
1981	9.224288595466934
1982	9.464617404404184
1983	9.44208201434508
1984	9.879087632575716
1985	9.214387324095018
1986	9.309829366360523
1987	9.475502563905803
1988	9.74444060283729
1989	10.155333757043742
1990	3.5629453681710213
1991	3.4229828850855744
1992	3.2948929159802307
1993	3.4019695613249774
1994	3.0461270670147953
1995	7.627118644067797
1996	10.982211910286157
1997	11.714507370054307
1998	12.325581395348838
1999	13.28560063643596
2000	14.035087719298245
2001	14.826752618855762
2002	15.298804780876493
2003	15.661707126076744
2004	16.8141592920354
2005	18.235294117647058
2006	17.96554552912223
2007	17.91530944625407
2008	17.689243027888445