In the foregoing determinations of market-value it was assumed that the mass of the produced commodities is given, i.e., remains the same, and that there is a change only in the proportions of its constituent elements, which are produced under different conditions, and that, hence, the market-value of the same mass of commodities is differently regulated. Suppose, this mass corresponds in size to the usual supply, leaving aside the possibility that a portion of the produced commodities may be temporarily withdrawn from the market. Should demand for this mass now also remain the same, this commodity will be sold at its market-value, no matter which of the three aforementioned cases regulates this market-value. This mass of commodities does not merely satisfy a need, but satisfies it to its full social extent. Should their quantity be smaller or greater, however, than the demand for them, there will be deviations of the market-price from the market-value. And the first deviation is that if the supply is too small, the market-value is always regulated by the commodities produced under the least favourable circumstances and, if the supply is too large, always by the commodities produced under the most favourable conditions; that therefore it is one of the extremes which determines the market-value, in spite of the fact that in accordance with the mere proportion of the commodity masses produced under different conditions, a different result should obtain. If the difference between demand and the available quantity of the product is more considerable, the market-price will likewise be considerably above or below the market-value. Now, the difference between the quantity of the produced commodities and that quantity of them at which they are sold at market-value may be due to two reasons. Either the quantity itself changes, becoming too small or too large, so that reproduction would have taken place on a different scale than that which regulated the given market-value. In that case, the supply changed, although demand remained the same, and there was, therefore, relative over-production or under-production. Or else reproduction, and thus supply, remained the same, while demand shrank or increased, which may be due to several reasons. Although the absolute magnitude of the supply was the same, its relative magnitude, its magnitude relative to, or measured by, the demand, had changed. The effect is the same as in the first case, but in the reverse direction. Finally, if changes take place on both sides, but either in reverse directions, or, if in the same direction, then not to the same extent, if therefore there are changes on both sides, but these alter the former proportion between the two sides, then the final result must always lead to one of the two above-mentioned cases.