Year	% of total
1970	45.03508140573356
1971	46.55703453390811
1972	46.135764847673876
1973	44.00494230205827
1974	45.86829048172118
1975	45.66283391742226
1976	47.290505368277564
1977	47.02317628245139
1978	51.226948057603686
1979	53.35812044279308
1980	54.426393971637545
1981	55.948377627867515
1982	57.5144305940643
1983	55.16544220763598
1984	59.11093819376506
1985	60.543700315413496
1986	59.26009009716048
1987	57.35518691326346
1988	57.765868546151786
1989	59.18763141706147
1990	81.96399345335516
1991	81.56618156618156
1992	80.64398097328943
1993	79.63537626066717
1994	78.44187963726299
1995	77.60668719753629
1996	77.41781800857551
1997	75.66191446028513
1998	73.75342465753425
1999	71.16745283018868
2000	69.17098445595855
2001	68.603916614024
2002	68.61404599129895
2003	67.7050222504768
2004	66.94915254237289
2005	65.86666666666666
2006	67.09429121231558
2007	68.27458256029685
2008	69.58083832335329