§ 4. The direct causal connection between the increased productive power of modern machinery and trade depression clearly emerges from a comparison of the fluctuations in the several departments of industry in different industrial countries. As modern machinery and modern methods of commerce are more highly developed and are applied more generally, trade fluctuations are deeper and more lasting. A comparison between more backward countries largely engaged in raising food and raw materials of manufacture for the great manufacturing countries is sometimes adduced in support of the contention that highly-evolved industry is steadier. But though Mr. Giffen is undoubtedly correct in holding that depressions are often worse in countries producing raw materials than in manufacturing countries,[156] this is only true of raw-material producing countries which produce for export, and which are therefore dependent for their trade upon fluctuations in demand for commodities in distant markets whose movements they are least able to calculate or control. Irregularity of climate, disease, and other natural causes must be a constant source of fluctuation in the productivity of agriculture. But those non-manufacturing countries which are little dependent upon commerce with manufacturing nations, and which are chiefly self-supporting, will of necessity retain a larger variety of agriculture and of other primitive industries, and will therefore be less at the mercy of some climatic or other injury than a country more specialised in some single crop or other industry. The specialisation impressed upon a backward country by commerce with advanced industrial countries, confining it to growing cotton or wheat or sheep or wine, exaggerates the irregularity imposed by nature upon its productivity, by making it subservient to the fluctuating demands of distant and wholly incalculable markets. The fluctuations brought about by irregular consumption and uncontrolled production in highly-evolved industrial countries are thus reflected with terrible force upon the more primitively-ordered parts of the industrial world. Thus does the character of modern machine-industry impress itself on the countries which feed it with raw materials.