case the exchange value of A, expressed in terms of B, rises and falls with the rise and fall of the labor-time required for the production of A.
Second case. Let the labor-time required for the production of commodity A remain constant. Then the exchange value of A, expressed in terms of B, falls and rises in an inverse ratio with the rise and fall of the labor-time required for the production of B.
Third case. Let the labor-time required for the production of commodities A and B rise and fall in equal proportion. Then the expression of equivalence of A and B remains unchanged. If through some cause the productivity of all kinds of labor were to decline uniformly, so that the production of all commodities would require an equally increased quantity of labor-time, then the value of all commodities would rise, though the expression of their exchange values would remain unchanged, and the actual wealth of society would decrease, because it would have to expend more labor-time on the production of the same stock of use-values.
Fourth case. Let the labor-time required for the production of A and B rise and fall, but not uniformly; that is to say, the labor-time required for the production of A may rise, while that required for B may fall, or vice versa. All of which can be reduced to the simple case where the labor-time required for the production of one commodity remains unchanged, while that required for the other rises or falls.
The exchange value of any commodity is expressed in the use-value of any other commodity, be it in integral units or in fractions thereof. As exchange value,
