or CEPAL) in 1950. In 1950, he released a study The Economic Development of Latin America and its Principal Problems that stated what is now known as the Prebisch–Singer hypothesis. German economist Hans Singer had separately arrived at a similar conclusion as Prebisch at roughly the same time, although his paper used a more empirical approach based on analysis of world trade statistics. The hypothesis begins with the observation that in the present world system the periphery produces primary goods to export to the center, and the centre produces secondary goods for export to the periphery. According to the hypothesis, as technology improves, the centre is able to retain the savings made, since it can retain higher wages and profits through developed unions and commercial institutions. At the periphery, companies and workers are weaker, and have to pass on technical savings to their customers in the form of lower prices. Prebisch pointed to the decline in the terms of trade between industrialised and non-industrialised countries, which meant peripheral nations had to export more to get the same value of industrial imports. Through this system, all of the benefits of technology and international trade would accrue to the centre. Due to Prebisch's influence the ECLA became the center of Third World activism in the UN, giving birth to the Latin American school of structuralist economics. While many scholars perceive Prebisch as supporting import substitution industrialization (ISI), in which a nation progressively changes its imports and internal production, focusing on industrialization, at the cost of imported "superfluous" goods in favor of capital and intermediate goods for a given period of time, Prebisch criticized protectionism, especially that practiced by Juan Perón in Argentina, since 1956 and ISI since at least 1963. He advocated industrialization and economic cooperation, including through trade, among developing countries. The International Institute of Social Studies (ISS) awarded its Honorary Fellowship to Raúl Prebisch in 1977. UNCTAD secretary-general Between 1964 and 1969, he served as the founding secretary-general of the United Nations Conference on Trade and Development (UNCTAD). Selected for his unparalleled reputation, he tried to forge UNCTAD into a body advocating the case of the whole developing world. His approach to development took a more trade-focused approach, advocating preferential access to the markets of developed countries and regional integration, building up trade between peripheral countries. Increasingly he stressed the extent to which developing countries had to bring growth by