Year	% of total
1970	1.7114722145011567
1971	1.7397227723234723
1972	1.7751573581612416
1973	1.7923529874911286
1974	1.848615494916138
1975	1.8741146052526507
1976	1.9650757942583479
1977	1.9217565292488508
1978	1.8845033674035339
1979	1.83168182590649
1980	2.0006046440657643
1981	2.1157597671524764
1982	1.966028399798236
1983	2.0690642486268453
1984	2.119309643927762
1985	2.1671485141788382
1986	2.142644536630157
1987	2.261260613476507
1988	2.2058037792998584
1989	2.2606001483915414
1990	5.607476635514018
1991	7.303370786516854
1992	6.770833333333333
1993	6.280193236714976
1994	6.467661691542288
1995	7.4074074074074066
1996	7.650273224043716
1997	7.291666666666667
1998	7.894736842105263
1999	7.042253521126761
2000	6.8807339449541285
2001	7.339449541284404
2002	6.722689075630252
2003	6.22568093385214
2004	7.053941908713693
2005	6.513409961685824
2006	6.538461538461539
2007	6.563706563706563
2008	6.614785992217899