As a basic asset, stock is not a tangible commodity, so there is no storage cost. However, its holding cost also consists of two parts: one is the occupation cost, which can be measured according to the market capital interest rate; The other is the stock dividend that may be obtained during the holding period. However, since this is the income from holding assets, when it is regarded as a cost, it can only be a negative cost. The net holding cost can be obtained by subtracting the last item from the previous paragraph. When the current item is greater than the latter item, the net holding cost is greater than zero; On the contrary, when the current project is smaller than the latter project, the net holding cost is less than zero.