These numbers are well-known, but they still shock every time you see them. China's internal imbalances make it such an extreme outlier.

This matters to the world because a country's internal imbalances must always be consistent with its external imbalances, and of course its external imbalances must always be consistent with the external imbalances of its trade partners. Because the balance of payments must always balance, both internally and externally, both of these statements are necessarily true.

But it doesn't end there. Given the size of the Chinese economy, the extent of its internal imbalances must also be a constraining factor on the internal imbalances of the rest of the world through their impact on their respective external imbalances. This may not necessarily be a bad thing, but it certainly must be understood by anyone who wants to understand other economies.

For example, if a group of countries implement policies that force domestic saving to rise above domestic investment, as long as they are able to control their external accounts, and as long as at least some of their trade partners don't, the rest of the world must "choose" to save less than it invests. There are good ways this can happen, and bad ways, but it must happen.

Similarly, if a group of countries implement policies that cause their manufacturing to grow faster than their GDP, and their consumption to grow more slowly, as long as they are able to control their external accounts, and as long as at least some of their trade partners don't, the rest of the world must "choose" to have manufacturing grow more slowly than GDP and consumption grow more quickly. Again, there are good ways this can happen, and bad ways, but it must happen.

The point is that we live in a highly globalized world in which some countries choose to have more open external accounts, while other countries (more determined to maintain economic sovereignty) choose to have more closed capital accounts. One consequence is that not only do the latter have more control over their domestic economies, but they also exert substantial control over the domestic economies of the former by constraining the range of policies they can pursue.

This, Joan Robinson explained, is ultimately unsustainable, and must eventually lead to a breakdown in global trade once the former decide to regain control of their external accounts. As she (and most economists back then) understood, very deep imbalances in more open economies are not the result of "free trade", as must economists believe today, but are rather the result of a trading system in which different major economies choose different levels of trade intervention.