Year	% of total
1971	67.49513396333738
1972	68.86392277460396
1973	73.19457629040325
1974	71.92817106365018
1975	73.78673085240189
1976	74.40996054791356
1977	74.79766894106831
1978	77.38962332506372
1979	80.42933049105125
1980	82.8370442487657
1981	84.78151809930394
1982	86.69254966562701
1983	88.74142471464994
1984	89.69825056317677
1985	90.7716601472188
1986	91.3178070195358
1987	91.02143812963071
1988	91.55986600798944
1989	91.41325940724232
1990	84.45300335458714
1991	84.46672947376074
1992	84.5346253538732
1993	84.38219436237047
1994	84.51613372373376
1995	84.74845540660846
1996	84.49355522489567
1997	85.07144894415384
1998	85.23115614568647
1999	86.29818877321821
2000	87.2355470727511
2001	89.12796022498843
2002	90.70416924625795
2003	91.25781986515446
2004	91.41246379170724
2005	89.77023574099275
2006	89.60793652103378
2007	89.67002139697559
2008	90.01348423293956
2009	86.51350523808283
2010	85.54525000863389
2011	85.73557281397103
2012	86.44176855537403
2013	86.7529806349824
2014	85.94171080472519
2015	85.79925785857269