Year	% of total
1960	28.756130182790905
1961	30.17345703912868
1962	28.064643279463937
1963	29.370885149963428
1964	28.942115768463072
1965	27.537148276952262
1966	27.382425742574256
1967	22.901891252955085
1968	19.898534385569334
1969	18.695106649937262
1970	19.730833934150443
1971	14.282521233795265
1972	8.952837729816146
1973	10.74243813015582
1974	8.620994866348026
1975	7.675137362637361
1976	5.870809484873262
1977	5.517909002904163
1978	7.4330861012576595
1979	6.724289481394667
1980	6.033428454953118
1981	5.239057239057239
1982	4.136375031336174
1983	5.321992709599028
1984	5.475649760282614
1985	10.462938185710463
1986	17.926228523368977
1987	22.05813953488372
1988	24.056130972268626
1989	23.224773091297386
1990	25.2145312880448
1991	25.84990647650222
1992	23.96839640795382
1993	26.251203319502075
1994	26.785380549682873
1995	26.70855000986388
1996	26.62600123102175
1997	26.078684468878855
1998	21.19737050359712
1999	23.130217006912073
2000	23.29490593577684
2001	19.85246171391333
2002	20.09276787075141
2003	20.57082782551223
2004	20.74012232415902
2005	19.508417595845426
2006	20.576449958643504
2007	18.60940136054422
2008	17.08342012667136
2009	19.097058614564833
2010	12.374505300353357
2011	16.80187487467415
2012	23.087955205309
2013	21.58772981099656
2014	22.131338994121492
2015	24.78994984954865
2016	22.140377358490564