Year	% of total
1971	93.22299356586522
1972	93.76432466608709
1973	88.55631821762124
1974	78.09660107334525
1975	73.48601029206284
1976	74.70876356897008
1977	76.97220251133804
1978	67.96973141113837
1979	64.28097021864457
1980	55.72457563088702
1981	54.72334509127423
1982	50.93015093015093
1983	48.90123944841058
1984	45.256415958724375
1985	41.39401303435326
1986	45.254372181295025
1987	45.39864332519841
1988	59.897408414041266
1989	64.12068658312052
1990	50.2089081592432
1991	55.099490890103134
1992	52.45790161235483
1993	48.479927244380924
1994	44.63236547971538
1995	49.24270685667388
1996	55.89644978905376
1997	49.6016487316385
1998	53.53996649192023
1999	63.87463183665354
2000	59.893150376785506
2001	50.336791877046
2002	49.54353308941068
2003	53.82701293056612
2004	60.50915988618779
2005	59.959617408120124
2006	55.6756402698631
2007	63.43899827770796
2008	67.62853195618565
2009	64.37880888130644
2010	65.68978868460759
2011	62.77642700011579
2012	66.02372683905122
2013	64.05254605329384
2014	64.25706881325013
2015	66.93502211000504