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Capital (economics)
In economics, capital consists of an asset that can enhance one's power to perform economically useful work. For example, in a fundamental sense a stone or an arrow is capital for a caveman who can use it as a hunting instrument, while roads are capital for inhabitants of a city.

Capital goods, real capital, or capital assets are already-produced, durable goods or any non-financial asset that is used in production of goods or services.

Earlier illustrations often described capital as physical items, such as tools, buildings, and vehicles that are used in the production process. Since at least the 1960s economists have increasingly focused on broader forms of capital. For example, investment in skills and education can be viewed as building up human capital or knowledge capital, and investments in intellectual property can be viewed as building up intellectual capital. These terms lead to certain questions and controversies discussed in those articles.

Separate literatures have developed to describe both natural capital and social capital. Such terms reflect a wide consensus that nature and society both function in such a similar manner as traditional industrial infrastructural capital, that it is entirely appropriate to refer to them as different types of capital in themselves. In particular, they can be used in the production of other goods, are not used up immediately in the process of production, and can be enhanced (if not created) by human effort.

There is also a literature of intellectual capital and intellectual property law. However, this increasingly distinguishes means of capital investment, and collection of potential rewards for patent, copyright (creative or individual capital), and trademark (social trust or social capital) instruments.

Within classical economics, Adam Smith (Wealth of Nations, Book II, Chapter 1) distinguished fixed capital from circulating capital. The former designated physical assets not consumed in the production of a product (e.g. machines and storage facilities), while the latter referred to physical assets consumed in the process of production (e.g. raw materials and intermediate products). For an enterprise, both were types of capital.

Investment or capital accumulation, in classical economic theory, is the production of increased capital. Investment requires that some goods be produced that are not immediately consumed, but instead used to produce other goods as capital goods. Investment is closely related to saving, though it is not the same. As Keynes pointed out, saving involves not spending all of one's income on current goods or services, while investment refers to spending on a specific type of goods, i.e., capital goods.

The Cambridge capital controversy was a dispute between economists at Cambridge, Massachusetts based MIT and University of Cambridge in the UK about the measurement of capital. The Cambridge, UK economists, including Joan Robinson and Piero Sraffa claimed that there is no basis for aggregating the heterogeneous objects that constitute 'capital goods.'

Political economists Jonathan Nitzan and Shimshon Bichler have suggested that capital is not a productive entity, but solely financial and that capital values measure the relative power of owners over the broad social processes that bear on profits.