Year	% of total
1970	7.902620557584977
1971	7.425556292471773
1972	8.97545935748071
1973	11.495546383544731
1974	11.945918110398162
1975	10.130830416371985
1976	11.26060186661179
1977	11.248078722791261
1978	13.157639759592549
1979	12.052626753994442
1980	11.06693059894065
1981	11.863608052254413
1982	10.16808666930448
1983	10.051690927499667
1984	9.994103595378268
1985	7.622426652828551
1986	7.396766112313304
1987	6.821027034748759
1988	7.255435135217075
1989	7.068356350343928
1990	4.233870967741935
1991	4.439746300211417
1992	4.670912951167728
1993	4.772234273318872
1994	5.188679245283019
1995	5.288461538461538
1996	5.386416861826698
1997	5.542168674698795
1998	4.872881355932203
1999	5.161290322580645
2000	41.351351351351354
2001	40.60846560846561
2002	41.7910447761194
2003	40.60446780551905
2004	37.43961352657005
2005	40.60052219321149
2006	39.076154806491886
2007	39.20099875156055
2008	41.03896103896104