130. Read the following passage, then answer the question below.

According to legend, coffee was discovered in Ethiopia by a goatherd named Kaldi, who noticed that his goats became lively after eating the red berries of a certain shrub. Whatever the truth of the tale, by the fifteenth century coffee was being cultivated in Yemen and exported from the port of Mocha, a name that survives in the vocabulary of coffee drinkers. Sufi monks drank it to stay awake during nighttime prayers, and from the monasteries the habit spread to the coffeehouses of Cairo, Mecca, and Istanbul. These establishments became centers of conversation, music, and news, and rulers sometimes viewed them with suspicion, since patrons discussed politics freely.

Yemen's monopoly was fragile. Arab merchants tried to protect it by exporting only roasted or boiled beans that could not sprout, but in the seventeenth century, a pilgrim is said to have smuggled fertile seeds to India, and the Dutch soon began planting coffee in Java. Europeans then carried the plants to the Americas; the French reportedly brought a seedling to Martinique in the 1720s. By the nineteenth century, Brazil had become the world's largest producer, and its plantations depended on enslaved labor until abolition in 1888.

The trade continues to shape economies. Today coffee is one of the most widely traded commodities, and millions of small farmers in tropical countries rely on it for income. Yet they are exposed to price swings they cannot control: when global supply rises, prices can fall below the cost of production, while a frost in Brazil can send them soaring. Certification schemes that promise a minimum price have helped some growers, although critics argue that the premium paid by consumers often fails to reach the farmers themselves. The story of coffee, then, is a story of how a plant moved across the world and of who benefits when it does.

What is the main purpose of paragraph 2?