Year	% of total
1960	74.49344866009767
1961	72.75348152733243
1962	73.22551467928564
1963	74.98480542512813
1964	74.74404504936321
1965	75.18439325894046
1966	77.2890476804452
1967	75.9352781868375
1968	77.81746146322392
1969	80.2502525781461
1970	81.83017167540537
1971	79.11746625008558
1972	78.22607077002371
1973	76.03950586617789
1974	74.86175795839979
1975	69.962635070176
1976	70.29042006832618
1977	68.79456932354832
1978	64.37363313486782
1979	65.8912631127779
1980	60.12571363418595
1981	55.14980362708266
1982	52.31005014237373
1983	48.32813101067023
1984	44.1086153917406
1985	43.4266348352962
1986	41.75551157724945
1987	40.00648716072786
1988	40.042882345035544
1989	39.09301733495724
1990	37.294957170813426
1991	35.52821961440979
1992	36.90834969881652
1993	36.877335384727594
1994	36.9024796082203
1995	36.8532278929887
1996	36.7164871066478
1997	35.637368824944794
1998	35.04731519533755
1999	34.84981229253483
2000	34.82918337265837
2001	33.98788812090221
2002	37.44624962167069
2003	36.521810320211124
2004	34.83201035455226
2005	33.81150917406153
2006	33.41258418676985
2007	32.452471951532644
2008	33.112640059417835
2009	31.983995335647116
2010	34.4232514038991
2011	34.21418704525978
2012	30.999155778788683
2013	30.01601560924334
2014	29.774747265134426
2015	25.11709613465313