Year	% of total
1960	79.27944331078322
1961	77.32761287782193
1962	71.03618719563907
1963	68.90464499196698
1964	68.58344973674375
1965	67.66464047125464
1966	67.62703985108193
1967	69.12395047482313
1968	68.41395434874325
1969	69.22637580372401
1970	69.9876103527597
1971	67.66302918989065
1972	69.62796188513278
1973	70.8268326379455
1974	68.61008304981176
1975	65.00361579427612
1976	69.22466162442231
1977	71.11573670773895
1978	69.10094335196196
1979	65.77572560264993
1980	64.76561959158306
1981	64.544190830369
1982	68.04110192203603
1983	66.94057402904706
1984	68.26025083545096
1985	71.37562006193228
1986	69.68552295830463
1987	69.36143404330706
1988	69.38861502570236
1989	67.44439608916358
1990	66.7463465777713
1991	67.04698352888518
1992	69.03009345670714
1993	68.30793359404488
1994	68.45249391920586
1995	67.8919243370432
1996	69.80940309541442
1997	72.05136330383006
1998	69.59774064490503
1999	70.81706548813462
2000	69.46326290235095
2001	71.80383968091236
2002	69.7739777662775
2003	70.01993546116283
2004	68.25817539887932
2005	68.18112114942768
2006	67.62940923656356
2007	67.5792870182821
2008	66.85097419240397
2009	64.13140864228005
2010	61.05375011444546
2011	59.75881494619944
2012	62.236579812626566
2013	60.83265376506635
2014	59.84684405263516
2015	59.74916853612227