goods. The development of the new colonies spurred a demand for equipment, machinery, and other goods which could only be sourced in France. The railroads and other infrastructure projects required French engineering expertise and a whole range of machinery/tools for their construction. Farmers and miners turned to France for the tools, chemicals, seed, etc. needed for their new enterprises. Some colonies were exporters of key raw materials to France. French West Africa was the primary source of coffee for the French market and a major source of cocoa. Sugar was supplied from Martinique, Réunion, and Guadeloupe. The colonies in north Africa, West Africa, and the Caribbean provided a range of tropical fruits like bananas, citrus, pineapples, and coconuts. Although the French government encouraged investment and development of the nation's overseas possessions, the government itself was reluctant to commit funds beyond their initial conquest and establishment. In 1900, the French parliament passed a law requiring the colonies to be fiscally self-sufficient. There was an active imperial lobby in France promoting greater investment and closer trading links between France and her colonies. This lobby argued for exclusionary tariff policy which would favor colonial trade. As protectionism returned in the 1870s and 1880s, subjecting imports to high tariffs, steps were taken to exempt the colonies. A customs union was established with Algeria in 1884, and with French Indochina in 1887. In 1892, a tariff-exemption zone was established between France and Algeria, Indochina, the old Caribbean colonies of the ancien régime, Gabon, Tunisia, and Madagascar. This allowed France and the chosen colonies to trade freely with one another. Another category of colonies exempted French imports from tariffs, but had to pay most favoured nation tariff rates when exporting their goods to France. This category included much of French West Africa, New Caledonia, Saint Pierre and Miquelon. Through this "highly preferential system", France was able to supply around 65.5% of the imports to her colonies. By the time the First World War broke out, the French overseas empire had become an important economic asset to the mother country. The empire absorbed 13% of French exports in 1913 and constituted 9.4% of her imports. This increased the national income by 5 to 6%. From 1902 the share of colonial trade was larger than France's trade with Germany, Belgium, and Luxembourg combined. The imperial markets were especially important as a prop for French industries which were in