Year	% of total
1971	99.98454532862085
1972	99.99484529556352
1985	97.25663732005884
1986	97.0552212407006
1987	97.15371951834496
1988	97.39435323219769
1989	97.26679232893397
1990	97.00507658928066
1991	97.02558512605674
1992	97.1545734911898
1993	97.11977184940214
1994	97.23903624171605
1995	97.26433977213475
1996	97.25290473604718
1997	97.30751240092863
1998	97.15872966772685
1999	97.1662216791979
2000	97.20731488353886
2001	97.15410337817345
2002	96.910142228797
2003	96.92671060497665
2004	96.66153646710065
2005	96.62279159161335
2006	96.95279431827672
2007	97.07304487171939
2008	96.53851267998938
2009	96.3958337700911
2010	96.35144841620573
2011	96.48398605359303
2012	96.6586087981408
2013	96.5747145209958
2014	91.74963605793465
2015	97.3821241260262