Year	% of total
1971	11.098344998025706
1972	11.898938428892572
1973	13.763606603066657
1974	14.227009074012228
1975	14.95450903634256
1976	16.1928162437882
1977	18.15168070161162
1978	19.77178864121451
1979	19.87621092418122
1980	20.85162413786715
1981	21.99186137923039
1982	23.180888372434445
1983	22.633978544514655
1984	21.192006295675384
1985	21.30072101783503
1986	20.407632490610368
1987	21.05506734253909
1988	20.646041285941028
1989	21.129181786354906
1990	20.736151351507697
1991	21.59448259094385
1992	22.466330884614532
1993	21.975678237202487
1994	18.63309324946154
1995	18.597598055597015
1996	20.028253787908337
1997	20.41243335301961
1998	19.51588132911097
1999	20.499251626856083
2000	20.856862941328746
2001	21.99654048006433
2002	22.233095181987878
2003	23.285903357396975
2004	22.57797874750384
2005	22.6761490939365
2006	21.33475188014665
2007	20.67407703000193
2008	21.408782115126698
2009	19.988773607299553
2010	21.946878599172678
2011	22.610506126430202
2012	23.053942417727026
2013	23.081634888900773
2014	23.471278025362164