The Prebisch-Singer hypothesis suggests that the prices of primary commodities, such as agricultural products and raw materials, tend to decline relative to the prices of manufactured goods over time. This theory was developed by economists Raúl Prebisch and Hans Singer in the mid-20th century, highlighting the challenges faced by developing countries that rely on exporting these commodities. According to the hypothesis, as economies industrialize, the demand for manufactured goods increases, leading to higher prices for these products compared to primary commodities. This imbalance can result in deteriorating terms of trade for countries dependent on exports of raw materials, making it difficult for them to achieve sustainable economic growth.