Year	% of total
1971	61.65624072467859
1972	61.15479735189871
1973	69.42255634041229
1974	67.6084961519356
1975	69.74301777525399
1976	68.8887136143469
1977	68.77444091501931
1978	67.4705600331461
1979	71.36971071343211
1980	73.57996119503596
1981	75.10582973462331
1982	77.9065346583511
1983	81.83155423943313
1984	83.59931906643783
1985	85.33424710963044
1986	84.89981817098366
1987	84.1918557940021
1988	85.59762781482434
1989	85.58066826951996
1990	87.31019344200256
1991	88.07502397328366
1992	88.04010369964853
1993	88.5331390427027
1994	89.96252738772877
1995	90.40663361122091
1996	90.32221000218533
1997	90.83086281940453
1998	91.28817813125104
1999	92.14496862583924
2000	93.1680591639337
2001	92.65303503499175
2002	93.12438030419682
2003	92.18355460447604
2004	92.56931708129068
2005	89.47043954291813
2006	89.27516812366939
2007	89.4857192347922
2008	92.86312466407479
2009	92.2833315603963
2010	91.95370010228443
2011	92.05514736018262
2012	92.02858254342011
2013	90.41027122259904
2014	90.24278752391184
2015	89.91130830412403