Year	% of total
1971	23.383188342160874
1972	25.464616379833156
1973	28.118596480138226
1974	32.59133678483367
1975	34.17672187663944
1976	37.80994311914285
1977	41.62675595687356
1978	43.88519303169741
1979	44.09117906445168
1980	42.89511527578049
1981	43.66996309686253
1982	41.72164830705151
1983	45.75274796024676
1984	46.87750905260461
1985	43.493337374715274
1986	47.13398262179113
1987	47.87572150820192
1988	53.30731026816936
1989	54.18111054418597
1990	55.459246609261456
1991	58.455670103092785
1992	59.048043615095935
1993	62.67835257194175
1994	65.87272523550423
1995	63.29552876755753
1996	65.39378725680652
1997	63.78766491289177
1998	65.49165738433447
1999	75.80217542073058
2000	73.86310096486956
2001	73.52793677367782
2002	75.42063182712694
2003	75.84136424213304
2004	75.46381544971132
2005	77.3982019457829
2006	79.50369519306871
2007	80.32569534515059
2008	79.38891753767227
2009	81.04683310487982
2010	81.65630027094592
2011	82.43970835670218
2012	83.15324465364061
2013	83.78117107440414
2014	84.54236030340438