flows can then be allocated to their appropriate category, without counting the same flow several times. In fact, the value theory applied in national accounts is nowadays strongly influenced by the valuation principles of ordinary business accounts and the prevailing social relations governing economic exchange, often fixed by law. Thus, for example, it is argued that no new value can result from a unilateral transfer of funds, i.e. where funds are provided without anything being provided in return. The implicit assumption made in national accounts, is that the account at the macro-level must be similar to that at the micro-level. Economic relations are regarded as broadly the same at the micro-level and the macro-level. An individual business buys and uses up inputs and produces outputs for sale; it has costs and revenues. Thus, in social accounting all transactors are treated in a similar way ("as if" they were a business). The accounts can be criticised for being eclectic in some ways, but that is not necessarily a problem; the aim of the exercise is to identify and categorise all flows, and the user can then reaggregate them in different ways. Persistent double counting problems However, even if a consistent system of accounting rules is devised that conceptually eliminates double counting, double counting may technically still occur to some extent. The first and most obvious reason is that, in actual accounting practice, boundary problems arise, because a flow of expenditures might be interpreted in different ways, from an accounting point of view. Sometimes, it will not be altogether clear which category a flow of expenditure belongs to exactly, it may not "fit" exactly into a category, or, it is technically impossible to separate out different flows in financial data, in such a way that is required by the social accounting system. This may mean that a flow is, in part or as a whole, inadvertently counted twice, because of difficulties with the data sources. We might be able to identify an expenditure quite easily, yet this expenditure may not tally with the corresponding income that should exist, insofar as we can identify it (or vice versa). In that case, we have to make some assumptions or imputations based on what we do know, or can observe. Yet, some statistical discrepancies may remain. Statisticians may not be able to keep track of fixed equipment or durables when they are resold by a