Year % of total reserves 1970 196.27439964779842 1971 178.14249699153874 1972 167.7098309697635 1973 122.6798962312112 1974 54.40866535017066 1975 79.3334775254067 1976 96.33871068932245 1977 91.91056564109799 1978 115.4981752872531 1979 101.12394162766196 1980 54.666937935117446 1981 70.54419032261917 1982 42.018787165254054 1983 61.190966519437076 1984 95.47652152194308 1985 133.21111488394055 1986 147.52838051876077 1987 156.36994089655946 1988 74.61437499537548 1989 45.25075943279536 1990 30.200275529239683 1991 34.31829261805181 1992 36.69068621491169 1993 36.19770348767982 1994 37.82549940269299 1995 30.499144712858563 1996 28.743469805571497 1997 31.601391995516902 1998 33.88846881006496 1999 33.04449591445798 2000 33.986450832290835 2001 33.1581265112559 2002 41.44594192545086 2003 30.26779818333037 2004 21.424814254331295 2005 10.125433069266547 2006 19.248695245812506 2007 4.196752815803214 2008 3.497903764831661 2009 3.550028434857507 2010 3.4564887805261866 2011 2.6990314525530494 2012 2.368235746233226 2013 1.735385734233585 2014 1.909542604011082 2015 3.26446270162306 2016 4.724662821503321 2017 2.6351825596026393 2018 7.872680561886693 2019 9.872743275184572 2020 11.004596448369954 2021 16.052978777443464 2022 16.81148892404186