Year	% of total
1970	7.483925838839071
1971	7.589172103221327
1972	7.842100589906541
1973	7.317718954382952
1974	9.138930215957874
1975	8.2950159390635
1976	8.031994821108594
1977	6.807724034937186
1978	7.961303453336519
1979	8.132404277546021
1980	7.0757109925273625
1981	8.786654674257646
1982	8.397357312326655
1983	28.25408326065255
1984	28.625453113848216
1985	27.485861033687716
1986	34.413198878356575
1987	30.068593024002826
1988	14.271953035087789
1989	23.07079809696136
1990	18.161683277962346
1991	18.25221238938053
1992	18.111964873765093
1993	18.013100436681224
1994	17.895878524945772
1995	19.3446088794926
1996	20.326864147088866
1997	20.8984375
1998	20.89009990917348
1999	21.341463414634145
2000	20.83000798084597
2001	21.774856203779784
2002	22.103533278553822
2003	21.064814814814813
2004	22.483766233766232
2005	21.30401819560273
2006	22.897196261682243
2007	23.72488408037094
2008	25.477707006369428