The world economy can be evaluated in various manners, according to the model used, and this evaluation can then be represented in various manners (for example, in 2006 dollars of the USA). It is inseparable from the geography and the ecology of the ground, and is thus slightly of a badly adapted term, since, whereas the definitions and the representations of the saving in world change considerably, they must with a minimum exclude any consideration from the resources or value based apart from ground. For example, whereas attempts could be made to calculate the value of the occasions of extraction currently unexploited in the territory not-claimed in the Antarctic, the same occasions over Mars would not be considered a part of the world saving – even if currently not exploited in an unspecified manner – and could be regarded latent value only as uncreated the intellectual property, such as has unconcealed previously the invention. Beyond the level of minimum to relate to the value in the production, the use, and exchanges it on the ground, the definitions, the representations, the models, and the evaluations of planet of the world economy change considerably.
It is common to the questions of limit of the world economy exclusively to the human economic activity, and the world economy is typically judged in monetary terms, even in the cases in which there is no effective market to help certain goods or services of valuate, or in the cases in which a lack of marks independent of research or co-operation of government establishing of the difficult figures. The typical examples are illegal drugs and other goods of black market, which by standard are a part of the world economy, but for what there is by definition no market legal of kind.
However, even in the cases in which there is a market clear and effective to establish a money value, the economists typically do not employ the rate of current or official exchange to translate the monetary units of this market into simple unit for the world economy, since the rates of exchange typically do not reflect the world value narrowly, for example whenever the volume or the price of the transactions is narrowly regulated by the government. Rather, of the evaluations of the market in a local currency are typically translated with a simple monetary unit by using the idea of the purchasing power. It is the method employed below, which is employed to consider the economic activity world in terms of truths dollars of the USA. However, the world economy can be evaluated and expressed in much more manners. It is not very clear, for example, which people of the world of 6.6 billion have the major part of their economic activity reflected in these evaluations.