Year	% of total
1971	24.67655387761273
1972	26.882897110707344
1973	29.228237051792828
1974	31.511094622983155
1975	32.62206017963409
1976	34.44660621513519
1977	39.844362570651036
1978	42.5670517681145
1979	44.15716873568307
1980	45.47945125310215
1981	47.0841315243426
1982	47.130112004585015
1983	46.663628231386625
1984	47.708552207118395
1985	48.56542729853612
1986	52.4410158350604
1987	52.18277490052202
1988	51.85335857303344
1989	53.60229116910862
1990	53.43061152034754
1991	54.81096835620984
1992	55.702097529578374
1993	59.07520985810276
1994	57.469475690778935
1995	60.59168121871823
1996	61.508443930527804
1997	62.045627417554016
1998	60.66479567055022
1999	62.21294558061439
2000	61.952267251921846
2001	61.45675619977161
2002	62.54925387301964
2003	62.4420226939689
2004	64.31644718231843
2005	64.99624529844579
2006	65.17708139022773
2007	64.5846374090852
2008	63.80707707408336
2009	65.52072458112153
2010	67.15478782486767
2011	65.30214419703972
2012	65.34475065372632
2013	65.26568680663945
2014	66.08947545658903