Year	% of total
1960	4.201117318435753
1961	3.9049919484702094
1962	5.526216522067144
1963	6.141107469380715
1964	6.368243243243244
1965	7.450729049831757
1966	8.61288812607271
1967	8.531157270029674
1968	8.187456926257752
1969	8.65472610798797
1970	9.566227730441518
1971	9.939540507859732
1972	11.24053581828771
1973	10.946681175190424
1974	9.790912746280659
1975	10.031668198998878
1976	9.723693077885818
1977	10.687663063734625
1978	13.372041875604824
1979	13.452174630684164
1980	15.58366402116402
1981	16.61992741669416
1982	16.83571599712483
1983	17.144975899147198
1984	17.406603279179457
1985	15.205032972030624
1986	14.055265123226288
1987	14.243172574084834
1988	14.3756118025451
1989	13.28098091892264
1990	17.149191567744577
1991	17.204015421115063
1992	15.733435444465327
1993	15.508162423807814
1994	15.920875420875419
1995	14.057040298002033
1996	17.40345114698386
1997	19.600775279131938
1998	20.33471368388204
1999	20.06446930374083
2000	21.46536585365854
2001	22.662009904371583
2002	23.49141414141414
2003	22.655278471974295
2004	23.76179473496976
2005	24.20815230530133
2006	24.33231115731116
2007	23.7280114884271
2008	29.219878333333334
2009	31.94646601016518
2010	34.02236703772418
2011	30.134337004720358
2012	32.60598947218665
2013	29.726317007327417
2014	28.41902029566525
2015	28.53317906948044
2016	26.158458691499526