Year	% of total
1971	51.264755480607086
1972	51.06382978723404
1973	56.34517766497462
1974	59.28449744463373
1975	60.38062283737025
1976	63.020833333333336
1977	69.06077348066299
1978	71.60493827160494
1979	70.12779552715655
1980	70.24673439767778
1981	70.31900138696255
1982	72.68170426065163
1983	73.25581395348837
1984	75.82417582417582
1985	76.01351351351352
1986	78.36065573770492
1987	80.82959641255604
1988	81.18586088939567
1989	82.0250284414107
1990	88.35274542429285
1991	89.49545078577337
1992	92.7477840451249
1993	91.3232104121475
1994	93.31495520330806
1995	93.51669941060904
1996	94.1983780411728
1997	97.02602230483272
1998	95.52329098608591
1999	97.62773722627736
2000	98.32735961768219
2001	99.00596421471172
2002	98.97260273972603
2003	99.30313588850174
2004	99.29105947223317
2005	99.57820738137083
2006	99.6940960538391
2007	95.43276007893995
2008	87.26502515223723
2009	88.27655310621243
2010	99.01606425702812
2011	98.83207070707071
2012	97.31296101159114
2013	95.81705355090784
2014	94.72411981082502
2015	92.68947015425888