Stock refers to a quantity of a commodity accumulated at a point of time. The quantity of the current production of a commodity which moves from a factory to the market is called flow.
The aggregates of macroeconomics are of two kinds some are stocks, typically the stock of capital ’k’ which is a timeless concept. A stock is always specified to a particular moment. Other aggregates are a flow concept, such as income, output, consumption and investment. A flow variable has the time dimension, it specified per unit of time.
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