Year % of total reserves 1970 33.71830665179483 1971 32.52147767883871 1972 26.22260707741223 1973 23.701558807009594 1974 20.782574664901812 1975 25.873432320466318 1976 16.775615732635483 1977 10.778807602388682 1978 10.6238496197622 1979 9.917689007207208 1980 16.923266331092528 1981 28.589353944215215 1982 33.5525881628409 1983 39.274670033805634 1984 44.46971596398501 1985 50.91809748490745 1986 55.12409335079249 1987 57.52449518895966 1988 78.1233811493259 1989 102.24202545599475 1990 149.32630259170836 1991 103.65716322096866 1992 77.28262311453656 1993 27.862025484611152 1994 20.533912594409312 1995 29.458162989348182 1996 33.269100523698015 1997 23.599742757232402 1998 18.991641893778585 1999 16.424230799734502 2000 12.80743382368075 2001 9.149739633445932 2002 8.475519313350185 2003 7.390565583315181 2004 6.617706354905571 2005 7.416269700312181 2006 14.216938952882431 2007 13.554229494595685 2008 17.89807391539409 2009 16.829895246246544 2010 19.32537769965662 2011 25.517480115299826 2012 30.60846989497525 2013 31.35516295081757 2014 26.76648179943354 2015 24.250371336423385 2016 24.37604880309547 2017 25.640954169627932 2018 27.798056569631527 2019 25.092229684983238 2020 19.2819578766661 2021 20.948872888122757 2022 25.31529124416015