Year	% of total
1970	5.102930360987142
1971	5.317838566466341
1972	5.405441621595018
1973	5.167357214686384
1974	6.374098706466443
1975	6.080297242945731
1976	6.004045681704382
1977	5.531628019719436
1978	6.330053499842254
1979	6.363048437147059
1980	5.797683517939477
1981	6.797968584577624
1982	6.0680237378050705
1983	6.4379316541200025
1984	6.573452109211775
1985	7.258841361928376
1986	7.1956725519251075
1987	7.697157528014155
1988	7.914148784627116
1989	7.224903283784437
1990	25.761772853185594
1991	25.64102564102564
1992	25.630810092961486
1993	25.58441558441558
1994	26.308900523560208
1995	24.37417654808959
1996	22.324966974900924
1997	19.767441860465116
1998	17.018633540372672
1999	16.11185086551265
2000	14.324324324324325
2001	14.721485411140584
2002	14.948453608247423
2003	14.1852286049238
2004	14.928909952606634
2005	14.20824295010846
2006	18.095238095238095
2007	17.956656346749224
2008	16.15575807787904