Year	% of total
1971	87.4762808349146
1972	88.45341667370555
1973	91.3389544688027
1974	88.67834867834867
1975	91.6351888667992
1976	92.2611065449669
1977	94.49354947906872
1978	86.88670263408443
1979	84.6067415730337
1980	85.33526679019307
1981	86.05715422687592
1982	86.59153100505542
1983	76.07369498464688
1984	73.62659827534938
1985	64.8249349216474
1986	49.40136160888958
1987	38.56545424530897
1988	48.17711423892146
1989	44.55093654944234
1990	43.7710565525619
1991	47.200565096463734
1992	52.068261470692256
1993	56.39668612577341
1994	62.29074454143073
1995	61.33300945682597
1996	62.11643345425829
1997	63.99056340437793
1998	56.48010589209929
1999	54.442774919777925
2000	60.804572204931276
2001	62.34258597320929
2002	62.82974130089386
2003	60.705846015775464
2004	62.55714488341898
2005	60.648303314994045
2006	61.709051134809954
2007	65.33053145654547
2008	64.97423051971455
2009	66.18748837662395
2010	68.73014466961132
2011	68.62108285117094
2012	70.15020671080265
2013	72.33714637352178
2014	69.49562713193347
2015	67.72439760681395