Year	% of total
1970	56.67966743353333
1971	56.80860932107811
1972	57.157947571413246
1973	54.130301372595824
1974	53.087639790185335
1975	56.95008871462866
1976	53.7400866691127
1977	53.852346785899826
1978	52.77963423375493
1979	52.932154601907385
1980	51.50578608697442
1981	51.50345363247635
1982	55.166970682510396
1983	55.29870263372098
1984	54.96923093894712
1985	54.031524453815116
1986	52.88916433540809
1987	52.65970086795227
1988	51.96577663694588
1989	52.19438537002233
1990	42.58943781942078
1991	41.78082191780822
1992	40.991420400381315
1993	37.44979919678715
1994	34.88865323435843
1995	33.59818388195232
1996	33.99778516057586
1997	33.81858902575588
1998	33.33333333333333
1999	33.97727272727273
2000	32.960893854748605
2001	31.79255918827508
2002	31.698973774230332
2003	31.007751937984494
2004	32.05574912891986
2005	31.5035799522673
2006	31.470230862697445
2007	31.2807881773399
2008	31.210986267166042