Year	% of total
1971	13.113953715457475
1972	12.586681865678731
1973	12.44517072331642
1974	12.194556139808228
1975	10.370427654473744
1976	11.243251130891581
1977	10.205151733630464
1978	9.353222369406208
1979	8.287292817679557
1980	7.908637386285826
1981	8.292823795543148
1982	8.412226129294021
1983	6.937349923597467
1984	9.784929232228986
1985	11.700898348678571
1986	10.292218824328916
1987	9.70251135028733
1988	9.893372107112565
1989	10.091507006005147
1990	10.198861292185823
1991	10.281157069478237
1992	14.172535211267606
1993	11.281412899712128
1994	8.551281122461301
1995	10.00327746043637
1996	4.319450209861169
1997	6.8669431678062995
1998	5.966991112991959
1999	4.565410303115222
2000	5.103768115942029
2001	5.4371345702315725
2002	5.124106389591936
2003	6.291227090092606
2004	4.014561837526901
2005	4.904940699684128
2006	5.4589416906909705
2007	6.297986382732146
2008	5.413135971968966
2009	7.412203188157274
2010	6.891155088852989
2011	3.7701827719039427
2012	5.471782861176169
2013	8.992484666993002
2014	10.178146082640383
2015	11.852152368257096