Year	% of total
1971	15.085135757017948
1972	14.903154867630889
1973	17.708756809496705
1974	21.78333074654664
1975	24.38477073827511
1976	24.364538127712336
1977	32.50146991572483
1978	32.892690513219286
1979	29.222822537552695
1980	17.944608604196922
1981	12.981476782542503
1982	8.749367088607594
1983	10.955698835274543
1984	8.33709329723768
1985	7.573479152426521
1986	5.309958278899237
1987	5.553152841449702
1988	5.032900586875334
1989	4.239316239316239
1990	6.412519119896458
1991	10.263385680722147
1992	6.7837465564738295
1993	6.479787057062053
1994	3.7630607274727
1995	2.8000605418495534
1996	4.789031193525576
1997	2.8579411647307706
1998	4.78392662832271
1999	1.2026329834549012
2000	0.6558867458925904
2001	2.1659969864389756
2002	2.1855209238792996
2003	2.284902859355838
2004	2.4195666447800397
2005	2.363485583056902
2006	2.310326069565774
2007	2.5455327692528322
2008	2.367872044506259
2009	2.415216636444307
2010	2.184678124089717
2011	2.071549773755656
2012	1.786218582321378
2013	1.5045240934277897
2014	1.1124208044791513
2015	1.441874436767798