Year	% of total
1971	35.51660813814878
1972	39.42083818393481
1973	41.1266846361186
1974	45.55192270154206
1975	50.443948638557515
1976	53.044777375641786
1977	52.21110239384603
1978	58.2435515002632
1979	52.334702424096
1980	57.935844210149035
1981	53.49043837226787
1982	55.777783330001995
1983	59.922811045837044
1984	58.37455423904291
1985	57.386357526159
1986	60.751127308666376
1987	61.67958308494067
1988	61.218619722925126
1989	59.259164861305806
1990	53.57700907309408
1991	51.02590028778098
1992	48.75963391136801
1993	47.091167734184395
1994	52.511027587659974
1995	44.5628185591929
1996	43.92768135150389
1997	47.74229370779675
1998	49.0844962260839
1999	45.374131899117536
2000	45.50820469186824
2001	42.00235527225826
2002	34.384866717685284
2003	30.34836612098198
2004	28.88843056952728
2005	27.303722963057485
2006	21.79696045802593
2007	20.251289242739528
2008	18.821454430685257
2009	17.498524765269615
2010	16.181855794321635
2011	16.266502835663633
2012	18.286419206582732
2013	16.18492832782871
2014	10.947408920848039
2015	10.148872847418188