Year	% of total
1960	0.17567157426134772
1961	0.1864957860060211
1962	0.19204413941865817
1963	0.20474052425179606
1964	0.20190277517792274
1965	0.20212093739448256
1966	0.22995580240909516
1967	0.22536257869004667
1968	0.23312937296846728
1969	0.23255174787994431
1970	0.28885661664348256
1971	0.2833247289682507
1972	0.2824603433584672
1973	0.30502295539227237
1974	0.2824429672543723
1975	0.31277118271414217
1976	0.3190838067619115
1977	0.32389349225274544
1978	0.3118408794653133
1979	0.34173267491769926
1980	0.3896601372484208
1981	0.4141260776234148
1982	0.5429859201163326
1983	0.5727694680342064
1984	0.6100787088214258
1985	0.6499423286081756
1986	0.7182447336221933
1987	0.7353420390935487
1988	0.7408123372329384
1989	1.5146036965602092
1990	1.8211882245872495
1991	1.39300605712446
1992	1.5368489640438319
1993	1.5704411123460937
1994	1.5902447994439597
1995	1.5715932224550977
1996	1.558875132329634
1997	1.6085650567118317
1998	1.642101763136398
1999	1.7207516345056066
2000	1.8224665967223816
2001	1.8862004725788055
2002	2.0904266047426114
2003	2.259854180197641
2004	2.5276719881676306
2005	2.804113407645612
2006	3.1045520107493196
2007	3.4919444068040604
2008	3.9612619640974165
2009	4.643521722977467
2010	5.301431897828847
2011	6.259818124055704
2012	7.208688441081907
2013	8.227153484690431
2014	9.151917224868313
2015	10.231384941116522