Year	% of total
1971	96.2081784386617
1972	95.89675711449371
1973	98.80534082923401
1974	80.42704626334519
1975	62.330487192365645
1976	40.57971014492754
1977	19.526627218934912
1978	27.028909787530473
1979	32.169648009232546
1980	35.32828282828283
1981	43.48288326600043
1982	51.034254509349665
1983	60.62394603709949
1984	54.514363885088926
1985	57.68548999746771
1986	63.988919667590025
1987	64.20077606709225
1988	70.70938215102976
1989	73.48637015781922
1990	76.50503832572561
1991	77.9620658510551
1992	78.98423817863399
1993	79.45877512264599
1994	83.19062047161113
1995	84.8977135980746
1996	86.09672318848482
1997	86.67486674866748
1998	87.23947256486602
1999	88.08010868136202
2000	87.18721497402547
2001	87.23420185684336
2002	91.25049084353692
2003	90.66129414553211
2004	86.98444368238926
2005	87.61986546443394
2006	89.41876994877022
2007	90.9994306712903
2008	93.00636228457206
2009	95.6913272374619
2010	94.4153577661431
2011	92.1571906354515
2012	90.77199384229432
2013	87.96823614341862
2014	88.89258081359472
2015	97.69028577820032