Year	% of total
1971	21.395272251807338
1972	21.2728876999591
1973	22.324074007860418
1974	24.978304220305393
1975	22.960219338733104
1976	22.43637264648359
1977	20.804878531812847
1978	17.448265854689048
1979	18.036916083073937
1980	18.94517604219258
1981	20.953856039108537
1982	22.07993177840998
1983	23.39710487642305
1984	22.769834939424268
1985	22.27442915902507
1986	21.63368712642878
1987	20.085954187274247
1988	20.076001571989213
1989	20.664025823023206
1990	20.135722506092794
1991	18.358164484490842
1992	17.589878189293763
1993	17.780513940656657
1994	17.602953216859614
1995	18.32396513893879
1996	16.92974117072995
1997	16.15739429179009
1998	16.63015128722255
1999	15.831035843728152
2000	15.854185986664252
2001	17.831063856689987
2002	16.520007105574944
2003	14.33360825276265
2004	15.223828310096902
2005	15.031716328311928
2006	14.657984820684764
2007	14.315246997376557
2008	16.188498208929943
2009	15.923347615790606
2010	16.128187518228607
2011	14.389456695787842
2012	16.882311910782537
2013	16.356625567405818
2014	17.98541635302681
2015	18.276017171406224