Year	% of total
1970	55.381003726560984
1971	54.33144891452512
1972	53.940636559568574
1973	53.726285142296405
1974	53.75076916306091
1975	54.330140062306796
1976	54.32509498832727
1977	53.59979159401814
1978	54.02372331425642
1979	52.79458821005547
1980	53.035150422255086
1981	52.91826143718254
1982	52.75201484163558
1983	60.55595121896234
1984	50.88499415037224
1985	49.91117183250412
1986	50.752402113975435
1987	50.3458531093216
1988	50.731838505029735
1989	49.46621735418217
1990	55.76848625629114
1991	53.41365461847389
1992	53.06679910603427
1993	54.711409395973156
1994	54.576810825152556
1995	55.906148867313924
1996	55.9687415790892
1997	54.45321307779031
1998	52.75590551181102
1999	52.10084033613446
2000	54.44613050075873
2001	58.30469644902635
2002	57.40190249702734
2003	56.173393124065775
2004	54.11001236093943
2005	53.188131313131315
2006	51.892591394370754
2007	48.641304347826086
2008	48.87295081967213