Since the value of money depends on these two factors, supply and demand, if we are to have a money of invariable value, we must evidently control one or both of these. It would be hopeless to attempt to control all the various conditions and forces which, we have seen, affect the demand for money. Fortunately it is not necessary. We cannot control the demand, but we have, or can have, complete control over the supply, and we can by this means maintain that constant relation between the supply of, and the demand for, money which is essential to its stability of value. _Necessity for Invariable Money Value._ Returning to the reasons for an invariable money value, they are best appreciated by considering the effects of one that is variable. While the statement of Mill, previously quoted, "that the money prices of all things should rise or fall, provided all rise or fall equally, is in itself and apart from existing contracts, of no consequence," is true, yet is it true only under the condition specified, that _all shall rise or fall equally_, and this condition in the case of a fluctuating money value never obtains. Aside from the exception which Mill makes of fixed money contracts, which can never adjust themselves at all to a changed money value,--and the exception is of enormous volume and importance,--the prices of many commodities are not adjustable quickly or readily to a change in money value, especially when such change is an increase. There is a persistency or inertia about prices that in many instances resists a reduction. Wages can never be reduced without friction and often strikes. The fact that commodities have fallen and that the lower wages will buy as much, or more, than the higher ones formerly did, is slow of appreciation; hence the employer caught between the difficulty of reducing his employés' wages and the falling prices of his products, is injured by an increased money value. When the change, on the other hand, is a decrease of money value, the employer will not as a rule advance wages until compelled to do so, and the labourer suffers meanwhile from the rising prices of commodities. When prices fall, the producers of a commodity are not apt to recognize that it is a general fall, a change in money value; but accustomed to regard money as invariable in value, as it should be, and, failing to see anything in the conditions affecting their own particular product that should lower the price, they delay or refuse to sell, hoping for higher prices; and all, or a large number, doing this, makes business dull. The great injury and evil of changing money value comes, however, through fixed money contracts. The enormous amount of bonded indebtedness, railroad, municipal, county, state, and national, makes the slightest change of money value of vast importance, and added to these is the aggregate volume of commercial and private debts.