Year	% of total
1971	19.72432126866962
1972	18.559768410126935
1973	19.04977932510311
1974	15.972760419464041
1975	17.334339169498392
1976	15.400077899905481
1977	17.064887031147602
1978	16.255230623294437
1979	17.07296475465713
1980	20.570280279986058
1981	21.46434204938798
1982	22.73715411877638
1983	22.293991698402092
1984	21.69594515652079
1985	23.92382523434958
1986	24.217906060786685
1987	26.841178060828586
1988	26.163565773140935
1989	26.67685871626545
1990	66.12274913366917
1991	65.41425610079841
1992	63.96043137519292
1993	65.28072498734004
1994	63.62669628122961
1995	64.78513622536778
1996	66.20665039834395
1997	66.62569642249176
1998	66.78456250709264
1999	68.79828891617862
2000	70.0898762375815
2001	69.24646001166376
2002	67.2479261868946
2003	63.70585751806277
2004	64.56777261937599
2005	63.82063480040517
2006	64.12221435481595
2007	66.2135449747239
2008	64.16412682619811
2009	66.03055515742571
2010	62.72230348159303
2011	64.58807571961557
2012	64.09825289979885
2013	64.43255775100155
2014	63.593483035692444
2015	63.33942750384094