In 1938, the year before the Second World War, the United States had, by far, the largest economy in the world in terms of gross domestic product (GDP). The five Allied Great Powers that emerged victorious from the war, along with the three Axis Tripartite Pact countries that were ultimately defeated made up the eight largest independent economies in 1938.

When values are converted into 1990 international dollars, the U.S. GDP was over 800 billion dollars in 1938, which was more than double that of the second largest economy, the Soviet Union. Even the combined economies of the UK, its dominions, and colonies had a value of just over 680 billion 1990 dollars, showing that the United States had established itself as the world's leading economy during the interwar period (despite the Great Depression).

Interestingly, the British and Dutch colonies had larger combined GDPs than their respective metropoles, which was a key motivator for the Japanese invasion of these territories in East Asia during the war. Trade with neutral and non-belligerent countries also contributed greatly to the economic development of Allied and Axis powers throughout the war; for example, natural resources from Latin America were essential to the American war effort, while German manufacturing was often dependent on Swedish iron supplies.

In the century between Napoleon's defeat and the outbreak of the First World War (known as the "Pax Britannica"), the British Empire grew to become the largest and most powerful empire in the world. At its peak in the 1910s and 1920s, it encompassed almost one quarter of both the world's population and its land surface, and was known as "the empire on which the sun never sets". The empire's influence could be felt across the globe, as Britain could use its position to affect trade and economies in all areas of the world, including many regions that were not part of the formal empire (for example, Britain was able to affect trading policy in China for over a century, due to its control of Hong Kong and the neighboring colonies of India and Burma). Some historians argue that because of its economic, military, political and cultural influence, nineteenth century Britain was the closest thing to a hegemonic superpower that the world ever had, and possibly ever will have. "Rule Britannia" Due to the technological and logistical restrictions of the past, we will never know the exact borders of the British Empire each year, nor the full extent of its power. However, by using historical sources in conjunction with modern political borders, we can gain new perspectives and insights on just how large and influential the British Empire actually was. If we transpose a map of all former British colonies, dominions, mandates, protectorates and territories, as well as secure territories of the East India Trading Company (EIC) (who acted as the precursor to the British Empire) onto a current map of the world, we can see that Britain had a significant presence in at least 94 present-day countries (approximately 48 percent). This included large territories such as Australia, the Indian subcontinent, most of North America and roughly one third of the African continent, as well as a strategic network of small enclaves (such as Gibraltar and Hong Kong) and islands around the globe that helped Britain to maintain and protect its trade routes. The sun sets... Although the data in this graph does not show the annual population or size of the British Empire, it does give some context to how Britain has impacted and controlled the development of the world over the past four centuries. From 1600 until 1920, Britain's Empire expanded from a small colony in Newfoundland, a failing conquest in Ireland, and early ventures by the EIC in India, to Britain having some level of formal control in almost half of all present-day countries. The English language is an official language in all inhabited continents, its political and bureaucratic systems are used all over the globe, and empirical expansion helped Christianity to become the most practiced major religion worldwide. In the second half of the twentieth century, imperial and colonial empires were eventually replaced by global enterprises. The United States and Soviet Union emerged from the Second World War as the new global superpowers, and the independence movements in longstanding colonies, particularly Britain, France and Portugal, gradually succeeded. The British Empire finally ended in 1997 when it seceded control of Hong Kong to China, after more than 150 years in charge. Today, the United Kingdom consists of four constituent countries, and it is responsible for three crown dependencies and fourteen overseas territories, although the legacy of the British Empire can still be seen, and it's impact will be felt for centuries to come.

Between 1688 and 1968, Britain was arguably involved in more wars than any other nation or empire on the planet. During this 280 year period, the British government's investment into it's military strength increased greatly, and this level of investment allowed Britain to become the most powerful nation in the world for the majority of this period. Inflation rates and fluctuation of the pound Sterling's value make it difficult to compare military spending over extended periods of time, however, if we look at when the largest increases occur over short periods of time, then we can see a correlation between Britain's involvement in major wars and also times of great empirical expansion. Rule Britannia Before the twentieth century, Britain was able to become the world's hegemonic power (or the closest thing to it) because of it's military and naval might. In the past, some historians argued that Britain rose to this status accidentally, however it was their investment in military and naval capabilities that allowed them to colonize other civilizations, protect trade routes, and eliminate competition or threats. For example, Britain lost one of it's largest sources of income when the US gained independence in the late 1700s, therefore the government invested five times more money into it's navy than into the army (in 1785), in order to protect it's other colonies and trade routes, and to expand into other parts of the world. In the nineteenth century, the largest influx of cash into the military came in 1815, the same year that Britain and it's allies finally defeated Napoleon. The end of the Napoleonic Wars marked the beginning of the 'Pax Britannica', (1815-1914) which was a century of relative peace between the major European powers, and further expansion of the British Empire. Twentieth Century There was a large increase in military expenditure at the turn of the twentieth century, as the British Empire pushed further into new territories, particularly in Africa (in what is now known as the 'Scramble for Africa'). However, the largest increases came directly after both World Wars. It is also important to note that new budgets were introduced for the Air Force in the First World War, and then for Central Defense following the Second World War. Unfortunately there is no correlating data for the years during the World Wars, as the country was in a state of national emergency during these times, and parliament's system for budget allocation was different than in traditional years. Following the Second World War, Britain's investment in all military branches has increased exponentially, and today, Britain has the seventh highest military budget in the world.

During the 19th century, the United States generally had a negative trade balance, importing more than it exported, particularly from the British Empire. This changed at the turn of the 20th century, and the U.S. consistently had a positive trade balance between 1896 and 1970. The greatest periods of fluctuation came during the world wars, as well as an observable decline following the Wall Street Crash of 1929.

While inflation rates increased the total value of imports and exports over time, the rate of growth did increase significantly from 1900 onwards. The early 20th century saw the U.S. move away from its traditional isolationist policies (apart from a brief period during the great Depression) and emerge as a global superpower. Following the Second World War, the U.S. used its economic power to maintain its influence across the globe, as it sought to suppress the expansion of communism.