Year	% of total
1970	4.242404363920327
1971	4.209517755925233
1972	4.215507428414909
1973	4.403890534638554
1974	4.623234164921094
1975	5.195147513803513
1976	5.369460401440475
1977	5.50833082823295
1978	5.400687277969482
1979	5.4066316416116145
1980	5.186108242430394
1981	5.671129277483217
1982	5.6718656332792925
1983	5.436941019776906
1984	6.01701870056239
1985	5.859863476400162
1986	5.613397400490213
1987	5.962963545150501
1988	5.650772497364849
1989	4.850876822548008
1990	8.051948051948052
1991	8.579088471849866
1992	8.421052631578947
1993	8.672086720867208
1994	8.375634517766498
1995	7.783018867924528
1996	7.943925233644859
1997	8.294930875576037
1998	8.222222222222223
1999	8.444444444444445
2000	8.843537414965986
2001	9.60591133004926
2002	8.616780045351474
2003	7.7894736842105265
2004	7.4074074074074066
2005	6.578947368421052
2006	6.5371024734982335
2007	6.878306878306878
2008	7.8244274809160315