EDWARD S. MASON 181 



cable coverings account for nearly 50 per cent of domestic use. There 

 appears to be no effective substitute for lead in these uses. Further- 

 more, the recovery of scrap lead from these uses is exceptionally high: 

 85 per cent for storage batteries and 90 per cent for cable coverings. 

 On the other hand, there is one use for which recovery is zero. Every 

 year 150,000 tons of lead are blown into the air from the exhaust of 

 gasoline engines and, with the expansion of high-compression engines, 

 this is the most rapidly increasing use. It can hardly be maintained 

 that passenger transport in the United States would be seriously 

 affected by a reduction in the compression ratios for private motor 

 cars. Furthermore, a denial of this use might well lead to the develop- 

 ment of substitutes. Are we then, under the guidance of the price 

 system, encouraging low-priority current uses of lead at the expense 

 of future high-priority uses? 



Impressive as this case for conservation may appear at first blush, 

 it tends to disintegrate on analysis. The figures on known reserves of 

 lead are of little significance, representing hardly more than working 

 ore inventories, to be expanded when needed. The estimate of inferred 

 reserves are notably inexact. New discoveries will no doubt be made, 

 particularly outside the United States in areas where prospecting, to 

 date, has not been intensive. The flotation process, introduced in the 

 1920's, made possible the exploitation of lower grade ores and new 

 technological developments may be possible. On the demand side it is 

 worth noting that the former very heavy consumption of lead in paints 

 has almost completely given way to titanium. This suggests that sub- 

 stitution may be possible in other uses. If the PMPC is correct in 

 its assessment of future supplies and requirements, a substantial in- 

 crease in the real price of lead is indicated which, in itself, can be 

 expected to stimulate the search for supplies and substitutes. Finally, 

 an expectation of even a substantial increase in the real price of a 

 metal is not, in itself, an argument for intervention. If the real price 

 of lead were to double over the next twenty-five years it would require 

 an interest rate of less than 3 per cent to provide an economic justifica- 

 tion for curtailment of present in favor of future use. To the best of 

 my knowledge, so rapid an increase in the real price of any material 

 is unknown. 



The case for conservation of oil, so heavily pressed in many quar- 



