Year	% of total
1960	94.42732405571995
1961	94.38922762388808
1962	94.49635620581748
1963	94.6816493649933
1964	94.78318705767028
1965	94.75366354012002
1966	94.65255590180705
1967	94.77874309678418
1968	94.76749367737537
1969	94.82589127039475
1970	94.71625840924143
1971	94.59207220671425
1972	94.27028438817831
1973	94.27621569133161
1974	93.61861856484967
1975	92.86413208520877
1976	92.90738705335617
1977	92.26092097264099
1978	91.65622437320239
1979	91.61144630688501
1980	91.02013873136389
1981	89.95916702517862
1982	89.16645245294627
1983	88.23645019722
1984	87.22276452475093
1985	86.07552586894495
1986	85.50313364060924
1987	85.15412721508882
1988	84.94219184925356
1989	84.8351278878303
1990	84.04462250814238
1991	83.45292391889177
1992	83.46183854626418
1993	83.31899572870513
1994	83.2717908568728
1995	83.00460822111295
1996	82.99403193537599
1997	83.25729921691885
1998	83.01211336244994
1999	82.88799045185725
2000	82.8941901533154
2001	83.23449279792095
2002	83.11799950782856
2003	83.43057874333095
2004	83.02436662236325
2005	82.71954214104446
2006	82.49553564982743
2007	82.85907776734973
2008	82.37333306483569
2009	81.49274897597014
2010	81.18542782385751
2011	81.74849146159845
2012	81.68459575460541
2013	81.45997169743215
2014	81.1078736432346
2015	79.0819006212285