Year	% of total
1971	58.283963253066474
1972	58.42513425377614
1973	60.98044624020634
1974	59.19864910032564
1975	61.10698526049638
1976	59.440112081215034
1977	64.92202974322629
1978	65.53390493502836
1979	64.90635906844541
1980	60.47466307213284
1981	56.10679583677246
1982	54.970785138009035
1983	52.941010171330326
1984	52.07951755225364
1985	53.08855793978513
1986	53.332367276640916
1987	54.69525332638286
1988	54.54787436306944
1989	58.379559360180444
1990	58.51363362948029
1991	59.39797200266983
1992	58.764414081197515
1993	58.57040387352864
1994	57.936651528871174
1995	59.28411092221396
1996	57.255654944681766
1997	58.918624937490904
1998	63.728769193144394
1999	61.00568974837214
2000	59.027159115585285
2001	57.21194443108768
2002	55.0019531686709
2003	56.59465626357547
2004	47.992865798501484
2005	46.89102785475761
2006	47.72020792281361
2007	49.06389155302085
2008	48.99822410472549
2009	48.070623718455806
2010	47.51590420949025
2011	48.26480979352498
2012	47.88482986633667
2013	49.37779479224999
2014	49.88027273396249