Year	% of total
1960	44.37270074844602
1961	45.074670187047836
1962	44.71869671588804
1963	43.61232133662191
1964	42.845848377890746
1965	43.22984536823858
1966	42.980522642595275
1967	43.036269049610596
1968	44.130759365249524
1969	44.30303974547154
1970	47.11932117072129
1971	48.17843922491503
1972	49.74929189620797
1973	50.342777458327056
1974	50.055381935999364
1975	50.75802023440082
1976	49.88648684741862
1977	51.55141950225597
1978	51.00536082474226
1979	49.416636992306614
1980	46.97068626453866
1981	44.91383464141693
1982	44.82967080218075
1983	44.40910407663248
1984	43.78455845479664
1985	43.69638838622155
1986	45.531370623301285
1987	44.746509861708475
1988	44.59213133823613
1989	43.88472118307095
1990	41.15343709687739
1991	40.791560682100375
1992	41.1098937748453
1993	40.940875958682895
1994	40.926288301535706
1995	40.49535569252375
1996	40.401474832059144
1997	39.44953548942951
1998	39.999009211726616
1999	40.415565032172964
2000	40.12902551931044
2001	40.48902495108058
2002	41.19265693151429
2003	41.989700545795394
2004	42.30239312338089
2005	42.50137908090228
2006	42.33868109352294
2007	41.4133033115167
2008	40.30256671352102
2009	41.71405727243655
2010	40.16940732856531
2011	40.44100976392568
2012	41.25014797352031
2013	40.73118718931133
2014	40.71265589172536
2015	42.79826195765826
2016	43.51014496874386