Year	% of total
1971	25.176160274112934
1972	26.175798647469108
1973	26.609082108659475
1974	25.543685631528053
1975	25.443897677922656
1976	24.676454105291405
1977	25.622263285646596
1978	25.832985525571257
1979	26.020202081110604
1980	24.963170356066733
1981	24.1730707622844
1982	24.099808354161055
1983	25.13011650315574
1984	23.124495884804926
1985	22.165845030052523
1986	21.32579386942792
1987	21.270971518747782
1988	20.6858917741707
1989	19.999396510817213
1990	17.472794879505273
1991	17.310425916991946
1992	17.591741666256606
1993	16.457143477954304
1994	16.21341344318558
1995	15.765819895823713
1996	15.681626092995247
1997	16.365889821089205
1998	16.6378670270197
1999	15.974514616831692
2000	16.44470398838111
2001	15.631997681409945
2002	14.793930410306796
2003	13.739388710452802
2004	13.164670808544749
2005	13.011697499321556
2006	12.752909275921178
2007	12.80904391246927
2008	13.120892711083116
2009	12.041125820835461
2010	11.106472214697629
2011	11.527235557120209
2012	11.807157630865625
2013	11.278110327903839
2014	10.050396862695932
2015	9.051554513435608