Year	% of total
1971	40.29116663387763
1972	28.92050209205021
1973	26.968871037153924
1974	33.238674780256936
1975	40.27251184834123
1976	37.01404437207409
1977	29.217002237136462
1978	16.69700087045976
1979	24.27285576136279
1980	8.824344932760294
1981	19.350640900514023
1982	22.978315562477537
1983	19.4102672889266
1984	19.41114916286149
1985	15.996359538874923
1986	22.470364526439294
1987	14.222392852156919
1988	11.63750616067028
1989	14.890659252526333
1990	11.261771097428468
1991	9.138188701803328
1992	7.422326526323165
1993	5.838472092986579
1994	6.341936299647358
1995	8.381304396688435
1996	8.169898265844482
1997	7.7231673567459715
1998	5.748900635188558
1999	3.9249658481324756
2000	6.278587578273961
2001	6.154071470415935
2002	6.8533110729912945
2003	6.23936811331561
2004	4.8040595894278875
2005	4.385878650801455
2006	5.856193510256447
2007	5.659166678290951
2008	4.824793455699808
2009	4.816906343922261
2010	3.470994596356616
2011	5.232994211204493
2012	5.246691599539701
2013	3.3729029380871625
2014	3.210626361908294
2015	2.665954095409541