Industrialization and unequal trade relationships. This is one of the biggest topics in economic history. In the 17th century, after the English Civil Wars, the creation of the Bank of England creates low private and public interest rates in England through the emergence of Europe's first reliable and stable bank. This leads to the financing of a number of economic and industrial ventures that culminate in the English industrial revolution, which later spreads to France, the Low Countries, and Germany.

While not always intentionally, Northwest European governments during this period also pursued generally pro-growth policies relative to the rest of the world. Of all the European heads of government, only Emperor Napoleon III was a well-educated economic historian, but all the major Northwest European governments pursued policies of liberalizing the flow of goods - either internally or externally - and creating exclusive trade zones. An important quote from Adam Smith illustrates the advantages of creating larger trade zones:

The greatest improvement in the productive powers of labour, and the greater part of the skill, dexterity, and judgment with which it is anywhere directed, or applied, seem to have been the effects of the division of labour.

Through creating a trade zone, this effect of increasing the division of labour could be more thoroughly exploited. First, a larger consumer market allowed for efficient factories, making full advantage of industrial advancements and division of labour, to service a larger market. Second, each part of an Empire or trade zone - especially if it was governed under the same law - could specialize in a product. This was harder to do without commercial networks like the British and French Empires, and the Zollverein in North Germany, since diplomatic disputes could easily sever business relationships and lead to economic collapse.

Over time, a combination of financing, scale (both in factories and consumer markets, allowing for greater specialization and division of labour), and advances in industrial equipment which increased productivity, allowed for the average productivity of industrial workers in Northwest Europe to exceed those in other parts of the world by a factor, of, eventually, 12-15 or more. However, modern economics were still unknown to governments at the time, and industrial revolution era growth was still slow by today's standards - estimates of economic growth across Northwest Europe during this period do not exceed 1.5%, and the early 1900s c. 1.7% growth in Austria-Hungary was considered "very fast" for the time period.

Division of labour and specialization, however, had a darker side - dependence. As productivity expanded and available markets were consumed by existing industries, demand for marketing abroad increased. This led to European merchants entering Asiatic markets like China, which inevitably created tensions when officials in those countries arrested European merchants for legal violations. In the case of China, the First Opium War started over the lawful detainment of British merchants over trading illegal drugs. This outraged the British government and led to an intervention. Superior British seamanship, which triumphed over a Chinese navy which had received little attention compared to the army for 500 years, created a treaty which demanded the opening of China's ports to trade.

China in India therefore took the role of producers of raw material and agricultural goods in the world market, while Europe adopted the role of the producer in the worldwide division of labor, which was created once Asian and African economies were forcibly opened by the West. Since trade barriers were low (Opium War unequal treaties specified that Chinese tariffs could not exceed 5%), Western manufactories had competitive advantage over Eastern workshops, and suppressed the development of new industries in Asia, trapping China and India in a subsistence and resource economy.

This all begs the question of why China didn't have an industrial revolution of its own. The market was there, so why did the same institutions fail to develop? The first answer lies in the credit supply. Political conflict led to restraint on the English crown's ability to default on debt, and private sector supervision of crown bonds, creating the Bank of England. No such restraint on the power of the Ming and Qing dynasties existed. Even if there had been a successful rebellion, it was unlikely to lead to a restrained monarchy - Chinese tradition placed a lesser value on the divine right of kings by bloodright, and would have legitimized the total deposition of the old dynasty and its replacement by a new one. The second is a darker mechanism, rooted in capital accumulation. In the age of empire, Western European nations acquired tens of millions of slaves, and tens of millions of other underpaid subjects, working in colonies and dependencies. This concentrated wealth in the hands of a few, who could invest in capital-intensive industrial ventures that would yield greater profit, but involved high starting costs. The labor market of China in the 13th to 18th centuries was relatively free, and this ironically restricted elite capital accumulation, sabotaging industrialization. Through these mechanisms, China turned from being a producer and exporter in the world economy to occupying the role of a raw resource producer in the new world system.

Sources:

Butler, Eric. The Enemy Within the Empire: A Short History of the Bank of England

Pomeranz, Keith. The Great Divergence: China, Europe and the Making of the Modern World Economy

Smith, Adam. The Wealth of Nations.

Wallerstein, Immaneul. The Modern World-System.

Here is a previous answer by /u/profrhodes to a similar question.