Year	% of total
1971	36.22490619506201
1972	36.20755839423491
1973	37.48217249736116
1974	37.51338182166391
1975	37.69131322668516
1976	38.368493388259765
1977	38.619935599088976
1978	39.5247498983258
1979	39.51057033830003
1980	40.36105366858343
1981	41.94229472506849
1982	43.21243431225519
1983	42.873793062158164
1984	43.17578876134426
1985	42.5786025686793
1986	42.421521250687725
1987	43.10055040252014
1988	42.844324314845764
1989	41.281174527014244
1990	40.656508631470146
1991	41.18037467181421
1992	39.42396488608841
1993	40.261728659733045
1994	39.146753437301214
1995	39.651364501404544
1996	39.41852574056133
1997	39.45457900155032
1998	38.55118960079543
1999	38.8994323077896
2000	38.23631543709159
2001	38.8976709468727
2002	38.014639617226806
2003	39.08267870120901
2004	39.93340247770571
2005	39.64842660827953
2006	38.9602522813808
2007	39.63581505212773
2008	40.966487951568254
2009	39.85679104045937
2010	39.59751226282023
2011	39.17406749768438
2012	38.702171961025776
2013	38.27411641824491
2014	39.789365843485506