Year	% of total
1960	87.02877131169062
1961	86.72576878932996
1962	86.90910680333064
1963	85.74242566363381
1964	84.44875149795789
1965	80.18256583744058
1966	76.8511967761471
1967	77.08996554882037
1968	76.24578883056876
1969	74.72714885582862
1970	74.46359923697497
1971	74.9893811745796
1972	72.37980692781622
1973	69.00350472282771
1974	67.20836331142479
1975	63.27461760950569
1976	66.08277194173075
1977	63.653348292348596
1978	62.64582319509614
1979	61.94284101092236
1980	62.939915083415535
1981	65.11608019036339
1982	66.20680226186636
1983	67.66259096914914
1984	65.32322005909788
1985	61.93752881512218
1986	62.261959744199544
1987	59.879125374434224
1988	58.626708754562614
1989	58.06130998193388
1990	58.73112389299735
1991	59.1460660736881
1992	57.124413497429124
1993	57.37846109089796
1994	56.52802239125675
1995	55.622600006756585
1996	54.96058588210085
1997	53.35860046604905
1998	54.119936637248244
1999	52.15448515505524
2000	53.14609313435131
2001	51.83953557913406
2002	52.683373599975255
2003	52.08423417378641
2004	50.42963156904297
2005	48.34589152322182
2006	47.16388613188522
2007	48.65235937714527
2008	44.99479807055708
2009	44.11355908645583
2010	43.642422472362
2011	44.856297799179224
2012	46.016468981174185
2013	47.24122949071404
2014	45.81019329901051
2015	44.262809161782116