The change of net inventory value is inventory investment. In the total investment, the proportion of inventory investment is not large, but because of its special volatility, it fluctuates greatly and has a great impact on the economic cycle, that is, inventory investment is a form of investment expenditure with great variability. In the American economy, 20%-40% of the decrease in gross national product is caused by the decrease in inventory investment. The marginal analysis method of enterprise fixed assets investment and residential investment is also applicable to the analysis of inventory investment.
In inventory investment, the most important thing is to divide voluntary inventory (planned inventory) and involuntary inventory (unplanned inventory). Inventory investment may be higher in two cases.
First, if the sales volume is unexpectedly low, enterprises will find that the shelves are full of inventory, which is involuntary inventory investment.
Secondly, if the enterprise wants to restore the exhausted inventory, its inventory investment will also be high.
These two situations obviously have different meanings for the total demand situation. The increase of involuntary inventory investment is the result of unexpected downturn in total demand; The increase of voluntary inventory investment is a reflection of the recent unusually high total demand. It can be seen that the acceleration of inventory accumulation may be related to both insufficient aggregate demand and excess aggregate demand. The key is to distinguish what kind of inventory investment it is.