According to the definition of the Brundtland Report sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Baumgartner and Quass broaden this definition and state that sustainability focuses on and looks for the balance between both human generations, and, humans and nature. They state three aspects of sustainability: “(i) justice between humans of different generations, (ii) justice between different humans of the same generation, in particular the present generation, and (iii) justice between humans and nature”. Thus sustainability should cover economic, social and environmental factors and it has to provide close interaction between these three points. However some analysts are sceptical about the usefulness of traditional economic and social indicators as measures of the sustainable development (Hammond et.al, 1995). For instance, GDP is the most commonly used indicator to assess the development and sustainability. However, this is challenged. According to Talberth (2010) GDP is inadequate to measure the sustainability and it lacks the ability to indicate the depletion and degradation of different types of capital such as natural, human, manufactured or social capital. Today, it is clear that there is a need to redefine the sustainability indicators. Nevertheless, there is neither sufficient body of research nor global consensus for such measures.

In this paper, we will examine concept of total capital stock and the difficulties of measuring it. We will first look at the factors of production and types of capital. Then we will clarify as to what is meant by weak and strong sustainability in economic theory. Finally, we will examine the difficulties of accurately quantifying the total capital stock.

In classical economic theory, there are three factors of production: land, labour and capital. Capital is used to produce other goods and unlike the raw materials it is not used immediately in the production process. Today capital stock has a broader definition. Ekins (1992) classifies capital stock in four different categories: (i) manufactured, (ii) human, (iii) social/organizational, and, (iv) natural capital. In addition, financial capital can be added to this list as a 5th category of capital stock (2008, p. 5). Each of these stocks is used to produce goods and/or services which are used as either final products or inputs in the production process.

Ekins et. al. (2003) defines the manufactured capital as the capital which includes tools, machines and infrastructure that is used for producing goods and not used up immediately. That is, manufactured goods can last more than one year and generally they cannot be seen as a part of final product. Human capita