Year	% of total
1971	5.435610661493513
1972	5.267515613889328
1973	5.001647802468567
1974	5.486359005245189
1975	5.036194935680063
1976	4.416196900440643
1977	5.29871440130924
1978	4.7671249837033205
1979	5.622375295735662
1980	5.553629001443792
1981	5.381442297917183
1982	6.117012854539439
1983	5.482814841478616
1984	5.169277105046018
1985	5.5348663878792035
1986	6.034258340802231
1987	6.559057786427805
1988	6.5893486836027915
1989	7.4540597961282264
1990	8.434311114324828
1991	8.977479855917398
1992	9.564679680845975
1993	9.649615821653505
1994	9.601740476331686
1995	10.795861609500713
1996	11.060701032838907
1997	11.775663430504704
1998	13.48970939811189
1999	14.199600808017632
2000	13.71951906802942
2001	13.84776624244964
2002	14.776369642171124
2003	16.863348706427978
2004	17.535504756996144
2005	16.446214998596474
2006	15.393586636597131
2007	16.05338094196236
2008	14.780431994595952
2009	16.60696600244383
2010	15.529158480782959
2011	14.513335495574392
2012	11.844548753436502
2013	9.677365731350871
2014	9.019151263786538
2015	9.100102039169263