Year	% of total
1971	32.965170092674214
1972	30.50572115151482
1973	31.46597047540731
1974	25.243779267423843
1975	26.985711255644784
1976	27.8887980156459
1977	29.684883912808374
1978	33.71921450707296
1979	35.179177487651856
1980	38.021937520011335
1981	37.17350786301644
1982	40.07646564771189
1983	44.724780166262285
1984	47.06105199951252
1985	45.773197648152966
1986	46.551247325481285
1987	46.23448431591123
1988	45.14387064719694
1989	44.95143417568453
1990	45.170387375717176
1991	42.781010106117776
1992	47.83860082202025
1993	48.02745490824418
1994	50.2662341600636
1995	50.53062276773353
1996	51.118472253497124
1997	51.85729333532577
1998	48.16841198311781
1999	48.64456742400551
2000	48.29375098699978
2001	46.30809443537911
2002	46.69422833587888
2003	44.943504048951866
2004	47.60632320971986
2005	37.79915228261027
2006	37.4785609911297
2007	36.85671157428999
2008	39.61869354336316
2009	37.49918409164622
2010	40.301643083475305
2011	43.06000108854822
2012	42.60565718320193
2013	42.58387078454954
2014	41.226415331437934
2015	39.51151742647878