Year	% of total
1970	76.10913979527382
1971	75.81611841543506
1972	75.66233426445804
1973	76.2848658523545
1974	73.64623900294175
1975	74.66993595494472
1976	75.1912536569104
1977	76.54559004590985
1978	74.98188289185887
1979	75.87059072141248
1980	77.34352348456294
1981	75.89171118283788
1982	76.92272375077377
1983	76.33223369744584
1984	76.11998875914092
1985	75.10029892966361
1986	75.34470112421691
1987	75.80671495265243
1988	75.07560089582783
1989	76.07203654542172
1990	42.43386243386244
1991	42.04545454545455
1992	41.30765331981754
1993	40.64676616915423
1994	35.89855706165282
1995	35.45337344220026
1996	37.677628907835974
1997	37.34025559105431
1998	39.257294429708224
1999	35.79277864992151
2000	38.91733723482078
2001	34.27435387673956
2002	31.231609920134513
2003	38.35616438356164
2004	35.17994338859685
2005	36.72248803827751
2006	36.59018987341772
2007	36.658841940532085
2008	38.02122820318423