Quarterly estimated refined copper spending (current $ mln.) Quarterly investment in equipment (current $ bln., Gordon)
01.01.1929 113.3 1.39
01.04.1929 105.9 1.41
01.07.1929 104.6 1.46
01.10.1929 82.9 1.32
01.01.1930 73.1 1.19