Year	% of total
1971	96.6787638843066
1972	96.8063872255489
1973	97.37455675911984
1974	95.78349559573482
1975	96.0486189770846
1976	97.00180389392274
1977	96.15775286166348
1978	96.58995620982019
1979	95.52576635641671
1980	95.44401397751443
1981	96.15320006719301
1982	96.94402254469597
1983	96.72556530334857
1984	95.6276713084241
1985	93.0008086578001
1986	86.75873675873676
1987	78.83143610521577
1988	78.37069045916623
1989	78.41120203896762
1990	77.92551910198969
1991	78.07389963182858
1992	76.88334998391385
1993	75.86353871858697
1994	74.72469129459316
1995	75.8365662401981
1996	76.323582407596
1997	77.12910911440896
1998	76.53967566229265
1999	75.5061643728861
2000	78.22002167025552
2001	76.6535549748094
2002	71.38890716494505
2003	66.48232225656878
2004	65.30134860961928
2005	65.98601262037567
2006	64.64723743036794
2007	66.28230253862631
2008	63.630470016207454
2009	60.95648765190121
2010	60.13222055513878
2011	58.88033557665714
2012	55.55504285533009
2013	53.26830062319784
2014	53.400864905518475
2015	55.915319066524646