In this article we will discuss about:- 1. Introduction to Prebisch-Singer Thesis 2. Assumptions in the Prebisch-Singer thesis 3. Criticisms.

Introduction to Prebisch-Singer Thesis:

There is empirical evidence related to the fact that the terms of trade have been continuously moving against the developing countries. On the basis of exports statistics concerning the United Kingdom between 1870 and 1940, Raul Prebisch demonstrated that the terms of trade had secular tendency to move against the primary products and in favour of the manufactured and capital goods.

This viewpoint has been strongly supported by H. W. Singer. The essence of Prebisch-Singer thesis is that the peripheral or LDC’s had to export large amounts of their primary products in order to import manufactured goods from the industrially advanced countries. The deterioration of terms of trade has been a major inhibitory factor in the growth of the LDC’s.

Prebisch and Singer maintain that there has been technical progress in the advanced countries, the fruit of which have not percolated to the LDC’s. In addition, the industrialised countries have maintained a monopoly control over the production of industrial goods. They could manipulate the prices of manufactured goods in their favour and against the interest of the LDC’s.


Except the success of OPEC in raising the prices of crude oil since mid 1970’s, there has been a relative decline in the international prices of farm and plantation products, minerals and forest products. Consequently, the terms of trade have remained unfavourable to the developing countries.

Assumptions in the Prebisch-Singer thesis:

The main assumptions in the Prebisch-Singer thesis are as under:

(i) As income rises in the advanced countries, the pattern of demand shifts from primary products to the manufactured products due to Engel’s law.

(ii) There is slow rise in demand for products in the developed countries.


(iii) The export market for product of LDC’s is competitive.

(iv) The export market for products of developed countries is monopolistic.

(v) Wages and prices are low in LDC’s.

(vi) The appearance of substitutes for products of LDC’s reduces demand for them.


(vii) The benefit of increased productivity is not passed by the producers of manufactured products in advanced countries to the LDC’s through lower prices.

(viii) The economic growth in the LDC’s is indicated by income terms of trade.

Singer has pointed out that the recent increase in debt problem of the LDC’s has imparted another twist to the hypothesis of secular deterioration of terms of trade for them in two ways. Firstly, a high proportion of proceeds from exports are not available for imports.

Secondly, there is an increased pressure upon the LDC’s to raise exports in order to repay external debts on account of IMF-induced adjustment polices. These pressures make the debt- ridden LDC’s to compete with other poor countries to enlarge their export earnings. It results in decline in the prices of export products of these countries.

Criticisms of Prebisch-Singer Thesis:

The Prebisch-Singer Thesis has come to be criticized on several grounds:

(i) Not Firm Basis for Inference:

The inference of secular deterioration of terms of trade for the LDC’s rests upon the exports of primary vis-a-vis manufactured products. In this regards, it should be remembered that the LDC’s export wide variety of primary products. Sometimes they export also certain manufactured products.

They, at the same time, do not import only manufactured products but also a number of primary products. It is, therefore, not proper to draw a firm inference about terms of trade just on the basis of primary versus manufactured exports.

(ii) Faulty Statement of Gains and Losses of Primary Exporters:


Jagdish Bhagwati has pointed out that the index of terms of trade employed in this thesis understates the gains of exporters of primary products. At the same time, there is over­statement of losses of primary producers.

(iii) Faulty Index of TOT:

The Prebisch- Singer hypothesis rests upon the index, which is the inverse of the British commodity terms of trade. This index overlooks the qualitative changes in products, appearance of new varieties of products, services like transport etc. The generalisation based on British terms of trade for the period 1870 to 1930, according to Kindleberger, is not true for the other developed countries of Europe.

(iv) Neglect of Supply Conditions:


In the determination of terms of trade, the Prebisch-Singer thesis considers only demand conditions. The supply conditions, which are likely to change significantly over time, have been neglected. The relative prices, in fact, depend not only upon the demand conditions but also on the supply conditions.

(v) Little Effect of Monopoly Power:

One of the arguments in support of this thesis was that the higher degree of monopoly power existing in industry than in agriculture led to secular deterioration of terms of trade for the developing countries. In this connection, it was also agreed that the monopoly element prohibited the percolation of benefits of technical progress to the LDC’s. The empirical evidence has not supported such a line of argument.

(vi) Inapplicability of Engel’s Law:


The secular decline in the demand for primary products in developed countries was attributed to Engel’s Law. But this is not true because this law is applicable to food and not to the raw materials, which constitute sizeable proportion of exports from, the LDC’s.

(vii) Benefits from Foreign Investment:

The deterioration of the terms of trade for the LDC’s is sometimes linked not to non-transmission of productivity gains to them by advanced countries through lower prices of manufactured goods, yet the benefits from foreign investments have percolated to the LDC’s through the product innovations, product improvement and product diversification. These benefits can amply offset any adverse effects of foreign investment upon terms of trade and the process of growth.

(viii) Difficult to Assess Variation in Demand for Primary Products:

The secular deterioration in terms of trade of the LDC’s during 1870 to 1930 period was supposed to be on account of the declining world demand for primary products. During that period, there were tremendous changes in world population, production techniques, living standards and means of transport. Given those extensive developments, it is extremely difficult to assess precisely the changes in world demand for primary products and the impact of those changes upon the terms of trade.

(ix) Export Instability and Price Variations:


The Prebisch-Singer thesis suggested that export instability in the LDC’s was basically due to variations in prices of primary products relative to those of manufactured products. Mc Been, on the contrary, held that the export instability in those countries could be on account of quantity variations rather than the price variations.

(x) Development of Export Sector not at the Expense of Domestic Sector:

In this thesis, Singer contended that foreign investments in poor countries, no doubt, enlarged the export sector but it was at the expense of the growth of domestic sector. This contention is, however, not always true because the foreign investments have not always crowded out the domestic investment. If foreign investments have helped exclusively the growth of export sector, even that should be treated as acceptable because some growth is better than no growth. It is far­fetched to relate worsening of terms of trade to the non-growth of domestic sector.

(xi) Faulty Policy Prescription:

Prebisch prescribed the adoption of protectionist policies by LDC’s to offset the worsening terms of trade. Any gains from tariff or non-tariff restrictions upon imports from advanced countries can at best be only short-lived because they will provoke retaliatory actions from them causing still greater injury to the LDC’s.

In the present W.TO regime of dismantling of trade restrictions, Prebisch suggestion is practically not possible to implement. There should be rather greater recourse to export promotion, import substitution, favourable trade agreements and adoption of appropriate monetary and fiscal action for improving the terms of trade in the developing countries.


(xii) Lack of Empirical Support:

The studies made by Morgan, Ellsworth, Haberler, Kindelberger and Lipsey have not supported the secular deterioration of terms of trade hypothesis, Lipsey has observed, “Although there have been very large swings in U.S. terms of trade since 1879, no long term trend has emerged. The average level of U.S. terms of trade since World War II has been almost the same as before World War I.” This objection of lack of empirical support against the Prebisch-Singer hypothesis is actually not very sound. A number of more recent empirical studies have, in fact, gone in favour of this hypothesis.

Despite all the objections raised against the Prebisch-Singer thesis, the empirical evidence has accumulated in support of it. The studies made by UNCTAD for 1950-61 and 1960-73 periods showed that there was a relative decline in the terms of trade of LDC’s vis-a-vis the developed countries. A study attempted by Thirlwall and Bergevin for the period 1973-82 indicated that there was an annual decline of terms of trade of LDC’s for all the primary commodity exports at the rate of 0.36 percent.

On the basis of their study related to exports of manufactured products for LDC’s to the advanced countries during 1970-87 period, Singer and Sarkar found that the terms of trade of LDC’s declined by about 1 percent per annum. Even the World Development Report 1955 recognised that the world prices of primary products declined sharply during I980’s and the terms of trade of LDC’s deteriorated during 1980-93 period.

According to the 1997 Human Development Report of UNDP, the terms of trade for the least developed countries declined by a cumulative 50 percent over the past 25 years. According to South Commission, compared with 1980, the terms of trade of developing countries had deteriorated by 29 percent in 1988. The average real price of non-oil commodities had declined by 25 percent during 1980-88 period compared with the previous two decades. The terms of trade of non-oil developing countries had deteriorated during 1980-88 period by 8 percent compared with 1960’s and 13 percent compared with 1970’s.