Annual % 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