The definite exception to this last conclusion is when the rise in prices is caused by general lowering of the productivity of industry. And so also it may be said that to the extent that higher prices are merely a mark of an increased cost of labor, or a drop in the efficiency of industrial enterprises, it does not follow that profits are growing. It is generally held that there is such a falling off in the efficiency of industrial enterprises, and an increase in the cost of labor in a period of very rapid business expansion and rising prices--especially toward the end of the period. Mitchell writes: "... Prosperity is unfavorable to economy in business management. When mills are running overtime, when salesmen are sought out by importunate buyers, when premiums are being offered for quick deliveries, when the railways are congested with traffic, then neither the over-rushed managers nor their subordinates have the time and the patience to keep waste down to the possible minimum. The pressure which depression applies to secure the fullest utilization of all material and labor is relaxed, and in a hundred little ways the cost of business creeps upward."[46] Then there are the indirect effects of the process of price change upward. Since profits generally are large, production tends to be stimulated and the volume of production increases. The turnover of industry is quickened somewhat. Plants are more fully utilized, and unemployment is small. More overtime is worked. The total earnings of the wage earners are likely to advance more than wage rates. The extent of the divergence between the increase in hourly or piece rates and weekly or yearly earnings is likely to vary greatly according to the nature of the causes of the price movement. When the price movement is just the reflex of a situation of depreciated paper money, for example, the volume of production may or may not be increasing. An interesting study of the divergence between hourly earnings and weekly earnings for the recent war period (Sept., 1914-March, 1919) is contained in one of the Reports of the National Industrial Conference Board. In the metal industries (those most directly affected by the war) the advance in weekly earnings for men was stated to be 103 per cent. as against 71 per cent. in hourly earnings. In the rubber and chemical industries the increases in weekly earnings were greater than in hourly earnings also, but not to the same extent as the above. In the textile industries the percentage increases were practically equal, while in the boot and shoe industry the increase in weekly earnings for men was less than the increase in hourly earnings. And for women in most industries the weekly earnings show the smaller per cent. of increase.[47] Of course, figures of yearly earnings would be more significant as a comparison.