Nogales border fence

The Nogales border fence divides a single city into two markedly different civic and economic worlds. A few feet separate residents who share a valley, similar backgrounds, and a common culture, yet the institutions on either side shape their access to safety, public services, political voice, and economic opportunity. The fence is not offered as the cause of those differences in itself; it makes visible the institutional boundary that the book argues is decisive.

A city divided by the border

The city of Nogales is cut in half by a fence. North of it lies Nogales, Arizona, where average household income is about $30,000 a year. Most teenagers attend school, most adults have graduated from high school, and residents live relatively long lives by global standards. Many people over sixty-five can rely on Medicare. Electricity, telephones, sewage, public health, roads connecting the city to other communities and the rest of the United States, and law and order are among the public provisions residents can generally take for granted.

The contrast is immediate on the south side, in Nogales, Sonora. Although the city lies in a relatively prosperous part of Mexico, average household income is about one-third that of its northern neighbor. Many adults have not completed high school, many teenagers are not in school, and mothers face high infant mortality. Poor sanitation and inadequate health care contribute to shorter lives. Roads are in bad condition, crime is high, and opening a business can mean risking robbery as well as struggling to obtain permissions and pay bribes. Corruption and government ineptitude are part of residents’ daily experience.

The political contrast is as important as the material one. Residents of Nogales, Arizona, can vote out their mayor, representatives, and senators, and participate in presidential elections; despite inefficiency and occasional corruption, they can regard government as an agent they may replace. Democracy is a much newer experience in Nogales, Sonora: until Mexico’s political reforms of 2000, the city, like the rest of the country, was under the corrupt control of the Institutional Revolutionary Party. The fence thus marks a boundary between differently structured political systems, not merely two levels of income.

What the boundary does—and does not—explain

The comparison rules out several tempting explanations. The two halves do not differ in geography, climate, or the diseases prevalent in the area; germs cross the border without encountering restrictions. Health outcomes differ, but the account attributes this to inferior sanitation and limited health care south of the border, rather than to a distinct disease environment.

Nor does the book explain the divide through ancestry or culture. The residents on both sides have similar backgrounds. After Mexico became independent from Spain in 1821, the area around Los dos Nogales remained part of Mexico, including after the Mexican-American War of 1846–1848. Only the Gadsden Purchase of 1853 extended the United States border into the region. During a later survey, Lieutenant N. Michler noted the pretty little valley of Los Nogales; communities grew on either side. Their inhabitants share ancestors, food, and music, and the book treats their cultures as substantially alike. The visible differences in health and prosperity therefore cannot be reduced to an ancient separation between distinct peoples.

Instead, the account identifies the border’s institutional division as the central explanation. Nogales, Arizona, is embedded in U.S. economic institutions that allow people more freedom to choose occupations and acquire education and skills, while giving employers incentives to invest in better technology and workers the prospect of higher wages. Its political institutions allow residents to elect representatives and remove them for misconduct. Those mechanisms, in turn, create pressure for politicians to supply services citizens demand, including public health, roads, and law and order.

In Nogales, Sonora, different institutions generate different incentives for residents, entrepreneurs, and businesses willing to invest. The contrast is not simply between a wealthy side and a poor side: it is a difference in how economic choices are constrained, how political authority is held accountable, and whether people can count on public order and basic services. The fence makes that institutional divergence legible in a place where geography and culture offer little explanation for it.

From a local comparison to a global argument

The book uses the two Nogaleses to challenge the geography hypothesis: the claim that climate or location accounts for enduring differences in prosperity. Montesquieu had argued that people in hot climates tended to be lazy and uninquiring, and linked those traits to both poverty and despotic government. Modern versions place more emphasis on tropical diseases and soils thought to be less suitable for agriculture, but preserve the idea that temperate regions possess a structural advantage. The Nogales comparison cuts against that account: the neighboring populations share a climate and disease environment, while their living conditions differ across the political boundary.

The argument extends beyond this city. The book invokes the contrast between North and South Korea and between East and West Germany before the fall of the Berlin Wall to make the same point: a boundary separating institutional systems can divide populations without a corresponding explanation in geography. It also notes that the tropics were not always poorer than temperate regions. At the time of the conquest of the Americas, areas that now include Mexico, Central America, Peru, and Bolivia contained the Aztec and Inca civilizations, politically centralized societies that built roads and provided famine relief. Geography, on this account, cannot supply a simple, timeless map of economic success.

The comparison also points backward in history. The book argues that institutional divergence took shape during the early colonial period and persisted into the present. Earlier differences between European monarchies that might initially have appeared small could acquire greater force as Atlantic trade expanded after 1600. English colonization at Roanoke began in 1585; the English East India Company was formed in 1600, the Dutch East India Company followed in 1602, Jamestown was founded in 1607, and Barbados was occupied in 1627. The book contrasts the growing power of English traders, who could not be wholly shut out of Atlantic commerce and pressed for restrictions on royal prerogatives, with imperial systems in which monarchs controlled trade more directly. Those conflicts contributed to institutional change in England, including the English Civil War and the Glorious Revolution.

The fence in a wider history of extraction

The same expansion of commerce that could strengthen more inclusive institutions in Britain also carried extractive institutions elsewhere. The Dutch East India Company pursued control over the spice trade in Southeast Asia: after securing an exclusive clove agreement with the ruler of Ambon in 1600, it used military power to displace competitors, seize a Portuguese fort in 1605, and impose restrictions on clove cultivation and trade in the northern Moluccas. On Ambon, Dutch rule intensified existing tribute and forced labor, tying households to the soil and obliging them to cultivate clove trees and provide labor. The account places these measures among the forces that curtailed local commerce and narrowed the prospects for independent development.

This larger history complicates any reading of the border as a self-contained explanation. The book links contemporary inequality not only to the persistence of extractive institutions or weak centralized states, but also to colonial expansion that imposed or strengthened those arrangements. In the Caribbean, it notes, plantation systems were built after the near-total collapse of Indigenous populations by importing enslaved Africans. In the Banda Islands, Dutch expansion destroyed the possibility of indigenous development through genocide, while its threat helped push other Southeast Asian city-states away from commerce. In India, meanwhile, a country that was the world’s largest producer and exporter of textiles in the eighteenth century faced a different reversal under British power.

Seen against that history, the Nogales border fence serves as a compact image of institutional divergence, not a claim that every inequality has one local or national cause. The residents’ shared valley and culture sharpen the contrast: prosperity and deprivation coexist within sight of one another because people live under different political and economic rules. The book’s conclusion is that those rules shape incentives and opportunities, while their origins and persistence must be understood through the wider history of institutional change, trade, and colonial power.