Year	% of total
1970	28.179278213243126
1971	28.793407341298327
1972	29.01730705694783
1973	28.82931277253366
1974	29.99794202774373
1975	29.98992311429951
1976	31.025412507354766
1977	30.94863201712567
1978	30.66801113878294
1979	26.047378403707917
1980	26.384876045423315
1981	27.035722994192753
1982	26.945980742072308
1983	27.14379149181391
1984	28.685644551473438
1985	28.533803826486654
1986	28.48795033400837
1987	28.079556401744828
1988	28.15727558909816
1989	29.804244914739847
1990	62.28070175438597
1991	61.135371179039296
1992	61.77777777777778
1993	62.727272727272734
1994	64.01869158878505
1995	68
1996	65.38461538461539
1997	63.84976525821596
1998	61.43497757847533
1999	58.54700854700855
2000	58.97435897435898
2001	57.377049180327866
2002	56.39999999999999
2003	50.204081632653065
2004	44.827586206896555
2005	39.1705069124424
2006	37.06896551724138
2007	35.684647302904565
2008	34.523809523809526