Year	% of total
1971	17.237590129483493
1972	21.33091904086441
1973	20.903354131958263
1974	14.985380086302946
1975	19.929702048860076
1976	21.32600850116166
1977	25.788512908066956
1978	32.11610180887668
1979	29.615708714544155
1980	30.815578096362856
1981	32.02453052125514
1982	33.86621930246535
1983	45.46792370904307
1984	46.529228975947504
1985	39.584761797226555
1986	36.815327118942086
1987	40.171012545414726
1988	37.40078705535278
1989	36.96940584774494
1990	37.29933763654025
1991	32.94173506290893
1992	34.1643479298079
1993	35.81605093966538
1994	38.53854488112173
1995	38.14999501874007
1996	38.73849491981333
1997	38.970513779207714
1998	41.03519223455497
1999	40.150958715197795
2000	38.43526580879208
2001	38.4438185569692
2002	42.01800572098674
2003	42.885888737493275
2004	46.13285410568275
2005	46.88588952240521
2006	47.13543102593067
2007	50.00042742780241
2008	47.33791531096843
2009	48.06714093144335
2010	51.50470692594804
2011	54.109020595310064
2012	54.03143734364865
2013	54.056653972585366
2014	56.05383578079681
2015	60.80822436661768