Consider: all prices are determined by the interaction of supply, the stock of goods available to be sold, and by the demand schedule for that good. If the government levies a general 20 percent tax on all retail sales, it is true that retailers will now incur an additional 20 percent cost on all sales. But how can they raise prices to cover these costs? Prices, at all times, tend to be set at the maximum net revenue point for each seller. If the sellers can simply pass the 20 percent increase in costs onto the consumers, why did they have to wait until a sales tax to raise prices? Prices are already at highest net income levels for each firm. Any increase in cost, therefore, will have to be absorbed by the firm; it cannot be passed forward to the consumers. Put another way: the levy of a sales tax has not changed the stock already available to the consumers; that stock has already been produced. Demand curves have not changed, and there is no reason for them to do so. Since supply and demand have not changed, neither will price. Or, looking at the situation from the point of the demand and supply of money, which help determine general price levels, the supply of money has remained as given, and there is also no reason to assume a change in the demand for cash balances either. Hence, prices will remain the same.
It might be objected that, even though shifting forward to higher prices cannot occur immediately, it can do so in the longer run, when factor and resources owners will have a chance to lower their supply at a later point in time. It is true that a partial excise can be shifted forward in this way, in the long run, by resources leaving, let us say, the liquor industry and shifting into other untaxed industries. After a while, then, the price of liquor can be raised by a liquor tax, but only by reducing the future supply, the stock of liquor available for sale at a future date. But such “shifting” is not a painless and prompt passing on of a higher price to consumers; it can only be accomplished in a longer run by a reduction in the supply of a good.
The burden of a sales tax cannot be shifted forward in the same way, however. For resources cannot escape a sales tax as they can an excise tax: by leaving the liquor industry and moving to another. We are assuming that the sales tax is general and uniform; it cannot therefore, be escaped by resources except by fleeing into idleness. Hence, we cannot maintain that the sales tax will be shifted forward in the long run by all supplies of goods falling by something like 20 percent (depending on elasticities). General supplies of goods will fall, and hence prices rise, only to the relatively modest extent that labor, seeing a rise in the opportunity cost of leisure because of a drop in wage incomes, will leave the labor force and become voluntarily idle (or more generally will lower the number of hours worked). [12]
In the long run, of course, and that run is not very long, the retail firms will not be able to absorb a sales tax; they are not unlimited pools of wealth ready to be confiscated. As the retail firms suffer losses, their demand curves for all intermediate goods, and then for all factors of production, will shift sharply downward, and these declines in demand schedules will be rapidly transmitted to all the ultimate factors of production: labor, land, and interest income. And since all firms tend to earn a uniform interest return determined by social time preference, the incidence of the fall in demand curves will rest rather quickly on the two ultimate factors of production: land and labor.
Hence, the seemingly common-sense view that a retail sales tax will readily be shifted forward to the consumer is totally incorrect. In contrast, the initial impact of the tax will be on the net incomes of retail firms. Their severe losses will lead to a rapid downward shift in demand curves,backward to land and labor, i.e., to wage rates and ground rents. Hence, instead of the retail sales tax being quickly and painlessly shifted forward, it will, in a longer-run, be painfully shifted backward to the incomes of labor and landowners. Once again, an alleged tax on consumption, has been transmuted by the processes of the market into a tax on incomes.
The general stress on forward shifting, and neglect of backward-shifting, in economics, is due to the disregard of the Austrian theory of value, and its insight that market price is determined only by the interaction of an already produced stock, with the subjective utilities and demand schedules of consumers for that stock. The market supply curve, therefore, should be vertical in the usual supply-demand diagram. The standard Marshallian forward-sloping supply curve illegitimately incorporates a time dimension within it, and it therefore cannot interact with an instantaneous, or freeze-frame, market demand curve. The Marshallian curve sustains the illusion that higher cost can directly raise prices, and not only indirectly by reducing supply. And while we may arrive at the same conclusion as Marshallian supply-curve analysis for a particular excise tax, where partial equilibrium can be used, this standard method breaks down for general sales taxation.