Year % of total reserves 1970 92.78880742517805 1971 85.55234843700859 1972 61.43505654264611 1973 46.55553199773452 1974 43.33233671672015 1975 53.196568839696674 1976 57.69094215730152 1977 93.50117549768848 1978 87.16086375138968 1979 87.7492950125735 1980 137.060511065784 1981 193.2479611934581 1982 260.6337231086056 1983 171.72775058056342 1984 110.18338470539814 1985 91.38060824130994 1986 76.48703799741595 1987 86.32509544692121 1988 118.95240175646835 1989 139.1176497130832 1990 135.8677962788889 1991 120.09557475614248 1992 100.1349189877254 1993 96.16089267987779 1994 108.5584873861816 1995 96.62545739517456 1996 76.46347759741343 1997 80.5401534211422 1998 80.28942582224833 1999 76.96333411972802 2000 72.82893339536068 2001 61.55952239290196 2002 59.68230789438918 2003 53.91637830351864 2004 49.67204183414117 2005 47.767839288251544 2006 37.94413243399588 2007 31.178434404889042 2008 32.72024856777292 2009 28.45791157028338 2010 32.88660510048544 2011 28.926066439877914 2012 29.447689523069023 2013 34.20474593317595 2014 35.31472191286204 2015 39.827417552717264 2016 35.01706358604293 2017 34.20369187778765 2018 34.39399776765316 2019 35.91749780098346 2020 28.68794915441921 2021 25.76232147850479 2022 28.10525200765766