How big should a country be?

Will we ever get it right?

The smallest human society is the family. The largest, historically, was the empire, although modern nation-states like China and India contain more people than any empires of the past. Much of human history can be explained as an attempt to find the optimal size for human organization.

Optimality, in this context, can have various definitions. Families probably deliver the greatest happiness, empires the greatest cumulative wealth and military force. Bands and tribes fall between these poles in both regards.

Before the invention of agriculture, the band was about as big as a human society could usefully get. Hunters can cooperate effectively in groups of dozens or scores, but not hundreds or thousands. Agriculture gave rise to cities and then to states. It also permitted the stratification of society by class. Freedom from labor allowed ruling classes to concentrate on extending their reach and power. Agriculture supported armies that served the purposes of the ruling classes.

The same economies of political scale that led from cities to states pointed in the direction of empires. The Mediterranean empires of the Greeks and the Romans, the Asian empires of China and India, the African empires of Songhai and Zimbabwe, and the American empires of the Aztecs and the Incas all displayed similar dynamics of expansion and consolidation.

But every empire in history eventually faded, breaking into smaller pieces. This suggests that by the time they did, they exceeded optimal size. The mechanisms of decline differed from empire to empire. Sometimes they were challenged from without; sometimes they eroded from within. Some lasted centuries, others barely decades.

The age of European exploration in the 15th and 16th centuries witnessed the rise of transoceanic empires. Portugal, Spain, Holland, England and France constructed far-flung empires of commerce, sustained by advances in maritime and military technology. The English empire, in particular, became as well an empire of settlement.

In Europe in the 17th century, from the wreckage of the Holy Roman Empire emerged modern nation-states, smaller and more nimble than empires, larger and more powerful than duchies and principalities. At first the European states were confessional, based on religion, but increasingly they looked to a sense of shared historical, cultural and ethnic identity. In the 18th and especially 19th century, the dominant ideology in Europe was nationalism: the belief that each people, or nation, should have its own state. Italian nationalism gave rise to modern Italy, German nationalism to Germany.

In the cases of Italy and Germany, nationalism was an additive force. In the Americas at this time, nationalism tended to be subtractive, or divisive. The American Revolution was an assertion of American nationalism, based on an American identity newly distinct from that of Britain. Similar sentiments led to the breakup of Spain's American empire.

The nationalists did not always win. The Confederate States of America represented, among other things, an attempt to assert and defend a unique Southern identity. Abraham Lincoln and the Union army defeated the attempt, but many Southerners still considered themselves a people apart, and they foiled efforts by the national government to compel the South to honor crucial portions of the federal constitution.

A dominant theme of world politics in the 20th century was the deconstruction of empires. World War I was the agent of the dismantling of the German, Austrian and Ottoman empires. World War II broke up the Japanese empire, and it fostered nationalist movements in Asia and Africa that dissolved the British and French empires. The defeat of the Soviet Union in the Cold War resulted in the breakup of the empire Russia had created over the previous three centuries.

A cursory glance at a world map at the dawn of the third millennium suggested that humans had settled on the nation-state as the optimal form of organization. The sovereignty of the nation-state was codified in the charter of the United Nations.

Yet a closer look told a more complicated story. In fact the very existence of the United Nations reflected a basic problem with nation-states, a problem that had given rise to the old empires in the first place. Sovereign nations are, by definition, outlaws to one another. They acknowledge no superior authority that can compel resolution of disputes among them. Their only recourse, in serious matters, is war.

The industrial revolution of the 19th century produced weapons that made war far more destructive than previously. Weapons continued to evolve in the 20th century, and the world wars were the most devastating conflicts in human history. In response to World War I, the victors of that conflict created the League of Nations, a supranational organization designed to remedy the problem of international anarchy. The refusal of America to join the league left it incapable of dealing with fascism in the following two decades. World War II taught the Americans the error of their ways, and the United States became a principal sponsor of the successor to the league, the United Nations.

The UN had some of the attributes of empire. It transcended nation-states, potentially daunting would-be aggressors. Its efforts were not without effect. It was created to prevent World War III, and that war hasn’t happened.

Yet the UN lacked the coercive authority that was the hallmark of empires. Whatever it did to prevent World War III, it didn’t prevent the many smaller wars that erupted in the decades after 1945.

Another approach to the nation-state problem emerged in Europe. A trade pact among several European countries in the 1950s evolved into the European Union of the 1990s and after. The EU was modeled in part on the United States, which, too, had taken sovereign states and formed them into a federal union.

The federation approach aimed to capture the advantages of large states while avoiding some of their disadvantages. For purposes of trade and defense, the member states acted as one. In matters domestic and personal, they acted more independently.

The formula wasn't perfect. In America, disputes over the location of the boundary between state and national authority gave rise to the Civil War. In Europe, national complaints against encroaching EU rules triggered Brexit, the departure of Britain from the union. This in turn prompted calls among Scots for Scotland to leave the United Kingdom and return to the EU, and in Northern Ireland to dump the UK for union with Ireland.

In all of this history, there was no single thread, no consistent preference for bigger or smaller, no track record answering the size question definitively. Empires and other large entities were powerful but unwieldy. Small states fostered a sense of belonging yet were vulnerable to big states.

The search for the optimal size did reveal one thing, though. Humans are simply difficult to please. Put them in a small state and they want something bigger. Put them in a large state and they want something smaller. The only thing they consistently want is whatever they don't currently have.