Year	% of total
1970	13.671735502236082
1971	13.444616330239272
1972	13.311719423640675
1973	13.316191889455062
1974	13.220135903369492
1975	13.021067322577096
1976	12.63981689347117
1977	12.343045830185183
1978	12.20188725181307
1979	11.962753816527282
1980	12.03768213116879
1981	11.775723884652331
1982	11.586453969545072
1983	11.24896490139856
1984	10.903601646764018
1985	10.914525099602459
1986	10.560335553780106
1987	10.884273076528293
1988	10.3865770110711
1989	10.459274706191763
1990	1.8843591029590885
1991	1.963378124347281
1992	2.036398078614438
1993	2.1217529248463216
1994	2.1668472372697725
1995	2.9422695738354805
1996	3.6499402628434887
1997	4.293525179856115
1998	4.925364790071001
1999	5.558288243974422
2000	6.372738839409194
2001	6.383783783783784
2002	6.756002233389167
2003	6.652003647872968
2004	6.58195020746888
2005	6.4174824483338275
2006	6.2706738493526135
2007	6.149938772733457
2008	6.162951096871802