World production of widely used metals grew rapidly until the early 1970's, as expressed in The Limits to Growth (Meadows et al., 1972), but then metal demand dropped sharply after 1973. Growth rates in production of each metal varied year by year or among metals.
The difference between supply-demand forecast and actual production during last 20 years was examined. Different patterns between the two for 16 metals were classified into four groups.
(1) The actual production of Co, Cr and Pt exceeded the projected trend that had been predicted in 1970.
(2) Iron accounts for more than 95% of all metals consumed. A significant proportion of Mn, Ni, W, Mo, Cr and Co produced is used in the steel industry. This group, composed of iron and related metals other than Co and Cr, shows a similar pattern.
(3) Growth rates of production of Cu, Zn, Ag, and Al continued to be low during the last 20 years, but the rates are not negative.
(4) Growth rates of production of Pb, Au, Sn and Hg are negative or zero. Large differences between actual production and predicted consumption prevailed during the 1970-1990 period.
When the lifetime of these metals calculated in 1970 are compared with those in 1990, static indices of Au, Hg, Ag, Sn, Zn and Pb which fall in the range of 10-30 year, have not changed very much. No tendency toward depletion of the resources has been found under the present condition. New reserves have been discovered in the last 20 years. A basic question in the long-term supply is how long the present situation continue.