Year	% of total
1971	53.66796610715552
1972	55.32013969732247
1973	55.929919137466314
1974	58.10072223306656
1975	64.37027593115381
1976	62.59153269926774
1977	62.14240609273044
1978	70.43340937006492
1979	69.39196263187566
1980	73.41626594187748
1981	65.05870935112156
1982	69.79562262642415
1983	73.02294905773294
1984	71.22052225928908
1985	70.0201099054727
1986	75.89927316902424
1987	78.11869002519182
1988	76.80635706613752
1989	75.03929314812456
1990	72.77122163039444
1991	74.31204791164346
1992	71.39480973025049
1993	70.9691685154747
1994	78.09706995806458
1995	70.80421417686932
1996	70.33946135163072
1997	73.80009910861946
1998	77.33127084430403
1999	73.86977181348232
2000	76.19885742068799
2001	78.81656915341047
2002	80.47758923293358
2003	83.42837306375071
2004	81.68177016032291
2005	80.49392266955911
2006	80.45088866649598
2007	81.98113634307428
2008	78.81662736943727
2009	83.11397775570113
2010	81.2460758446234
2011	81.74638564364774
2012	83.27073053237335
2013	82.68398996387803
2014	79.22128320110383
2015	80.87601000199268