Year	% of total
1960	10.28774057920732
1961	10.417273099409893
1962	10.563536863482605
1963	10.69897763197213
1964	10.717281529753095
1965	10.156420384109673
1966	10.760925150397561
1967	10.773630293019915
1968	11.547571054747644
1969	11.806780215198803
1970	12.514532782244506
1971	12.41596762576194
1972	12.125665998206797
1973	11.200832673798557
1974	11.366349153127969
1975	10.984804513292504
1976	10.331070228086583
1977	10.280357020489019
1978	10.080667207957429
1979	10.551632901670558
1980	10.46264778924894
1981	9.977854097848391
1982	9.294717665702416
1983	8.703711755459203
1984	9.373513441124592
1985	8.947858010994306
1986	8.238189628015107
1987	8.64720450349507
1988	8.200487939386022
1989	9.545230795167765
1990	10.619951498531512
1991	10.722421601878782
1992	11.160477418366705
1993	11.539196587660133
1994	12.453747625912657
1995	12.908049305178132
1996	12.771856791747568
1997	13.840930693392725
1998	14.516599197216653
1999	15.533423469237883
2000	15.859637514846087
2001	16.659305418264715
2002	17.302171244848722
2003	17.283798703548953
2004	18.183182912083065
2005	18.684735140595667
2006	19.625973650982953
2007	20.955228253541552
2008	21.393705043529017
2009	22.001055405473117
2010	22.75473078444497
2011	23.52287649904127
2012	24.77300783582926
2013	23.3710531261122
2014	23.2131079671876
2015	25.334390690992958