The scenario presented involves a situation where the supply of final goods is perfectly elastic and stable over a short timeframe. In this context, aggregate output is solely determined by the level of aggregate demand. This outcome is dictated by the principle of Effective demand.
In economic theory, 'Effective demand' posits that the level of output is contingent upon the prevailing demand, particularly when supply is perfectly elastic, enabling prices to remain static as output adjusts to fluctuations in demand. This principle aligns with Keynesian economics, which highlights demand-side influences on economic results.
The correct terminology to complete the statement is Effective demand.

In an economy, exclusion of _______ may lead to under estimation of the value of Gross Domestic Product (GDP).