Year	% of total
1971	9.663642644756779
1972	9.119952432875596
1973	8.549103215644278
1974	7.249961881412014
1975	7.397427598428183
1976	6.4289984041314145
1977	6.46997679226554
1978	6.641829363943685
1979	5.881007513613351
1980	5.871943938040136
1981	6.180013658150396
1982	7.571351320208001
1983	9.12002051708823
1984	8.997687788562015
1985	8.679043475300679
1986	9.26473137121679
1987	9.181942129702605
1988	9.360605401831993
1989	8.789596390209379
1990	10.041703674223836
1991	10.9140364353511
1992	12.353926078753863
1993	13.119840824407028
1994	13.908733744085872
1995	16.76195593165132
1996	17.999823641534057
1997	18.32261053889645
1998	18.224142603882218
1999	18.926064690218798
2000	18.85519643878159
2001	17.743729211405718
2002	16.46670653366724
2003	12.763300847189754
2004	13.333393873956878
2005	14.926273036596871
2006	17.22749635038387
2007	18.94874179408957
2008	20.109546174294525
2009	19.46198107307085
2010	15.924258360752672
2011	15.887801106751754
2012	15.827492520078396
2013	15.399268755216703
2014	14.54516332872001
2015	14.874694509590897