Year	% of total
1970	58.14002936096718
1971	58.50462611160173
1972	65.35736381086865
1973	64.33297813999015
1974	53.709824896745005
1975	59.109649168928634
1976	72.08814661893052
1977	60.70429565872084
1978	63.1992371269247
1979	67.36257977154045
1980	57.96577345616857
1981	71.55771341588537
1982	65.2965585686989
1983	55.66817005650522
1984	72.60263715871025
1985	71.66889810111687
1986	66.35489744900856
1987	67.02961956420714
1988	69.89361985500197
1989	66.41106653780284
1990	78.85952712100139
1991	78.29787234042553
1992	78.60394537177542
1993	79.30513595166163
1994	78.64823348694317
1995	77.37003058103976
1996	77.62345679012346
1997	77.19568567026194
1998	77.53164556962025
1999	73.46938775510205
2000	72.99843014128729
2001	73.99030694668821
2002	73.87687188019967
2003	72.59380097879283
2004	78.59778597785979
2005	80.0376647834275
2006	81.07074569789675
2007	82.11538461538461
2008	84.2911877394636