Year	% of total
1970	46.269271174147356
1971	52.53989832071974
1972	46.687983032310186
1973	49.56754632218893
1974	50.166007167020354
1975	48.47314056932998
1976	46.64157222889452
1977	52.67860519839942
1978	50.89992608900569
1979	51.539958399133226
1980	51.179592627503276
1981	52.18199635893984
1982	51.10255843195197
1983	53.08389699182685
1984	57.10628908788677
1985	56.57608341462124
1986	53.08881797844587
1987	50.38672644268978
1988	53.80990191492234
1989	53.43254412218998
1990	89.15470494417863
1991	86.49885583524028
1992	84.16848220769789
1993	81.95697432338653
1994	80
1995	80.86500655307994
1996	81.37384412153237
1997	82.30318802862719
1998	83.36507936507937
1999	84.44034440344403
2000	85.1400730816078
2001	82.31003039513678
2002	81.12472160356347
2003	79.73568281938326
2004	79.62962962962963
2005	79.15644923982344
2006	78.66995073891626
2007	78.46003898635477
2008	78.32369942196532