Factors of production
In contrast, many economists today consider "human capital" (skills and education) as the fourth factor of production, with entrepreneurship as a form of human capital. Yet others refer to intellectual capital. More recently, many have begun to see "social capital" as a factor, as contributing to production of goods and services.

Entrepreneurship: In markets, entrepreneurs combine the other factors of production, land, labor, and capital, to make a profit. Often these entrepreneurs are seen as innovators, developing new ways to produce new products. In a planned economy, central planners decide how land, labor, and capital should be used to provide for maximum benefit for all citizens. Just as with market entrepreneurs, the benefits may mostly accrue to the entrepreneurs themselves.
The sociologist C. Wright Mills refers to "new entrepreneurs" who work within and between corporate and government bureaucracies in new and different ways. Others (such as those practicing public choice theory) refer to "political entrepreneurs", i.e., politicians and other actors.
Much controversy rages about the benefits produced by entrepreneurship. But the real issue is about how well institutions they operate in (markets, planning, bureaucracies, government) serve the public. This concerns such issues as the relative importance of market failure and government failure.
In the book Accounting of Ideas, "intequity", a neologism, is abstracted from equity to add a newly researched production factor of the capitalist system. Equity, which is regarded as part of capital, was divided into equity and intequity. Intequity means capital of ideas.  Entrepreneurship was divided into network-related matters and creating-related matters. Network-related matters function in the sphere of equity, and creating-related matters in spheres of intequities.

Natural resources: Ayres and Warr (2010) are among the economists who criticize orthodox economics for overlooking the role of natural resources and the effects of declining resource capital. See also: Natural resource economics

Energy: Exercise can be seen as individual factor of production, with an elastication larger than labor. A cointegration analysis support results derived from linear exponential (LINEX) production functions.

Cultural heritage: C. H. Douglas disagreed with classical economists who recognized only three factors of production. While Douglas did not deny the role of these factors in production, he considered the "Cultural heritage" as the primary factor. He defined cultural inheritance as the knowledge, techniques, and processes that have accrued to us incrementally from the origins of civilization (i.e., progress). Consequently, mankind does not have to keep "reinventing the wheel". "We are merely the administrators of that cultural inheritance, and to that extent, the cultural inheritance is the property of all of us, without exception. Adam Smith, David Ricardo, and Karl Marx claimed that labor creates all value. While Douglas did not deny that all costs ultimately relate to labour charges of some sort (past or present), he denied that the present labour of the world creates all wealth. Douglas carefully distinguished between value, costs and prices. He claimed that one of the factors resulting in a misdirection of thought in terms of the nature and function of money was economists' near-obsession about values and their relation to prices and incomes. While Douglas recognized "value in use" as a legitimate theory of values, he also considered values as subjective and not capable of being measured in an objective manner.
Peter Kropotkin argued for the common ownership of all intellectual and useful property due to the collective work that went into creating it. Kropotkin does not argue that the product of a worker's labor should belong to the worker. Instead, Kropotkin asserts that every individual product is essentially the work of everyone since every individual relies on the intellectual and physical labor of those who came before them as well as those who built the world around them. Because of this, Kropotkin proclaims that every human deserves an essential right to well-being because every human contributes to the collective social product: Kropotkin goes on to say that the central obstacle preventing humanity from claiming this right is the state's violent protection of private property. Kropotkin compares this relationship to feudalism, saying that even if the forms have changed, the essential relationship between the propertied and the landless is the same as the relationship between a feudal lord and their serfs.

See also: 

References: 

Further reading: AP U.S. History (condensed). 2007.
"Produktionsfaktoren" (in German). Google Knol. Archived from the original on 2010-01-23. Retrieved 2010-02-16.

External links:  Media related to Factors of production at Wikimedia Commons