Full blog here.
Economic theory shows that when a sales tax is imposed, the cost is borne partly by the purchaser (the consumer) and partly by the seller/producer.
The percentage which is borne by each depends on the price elasticity of demand*. At one extreme, for goods for which the consumer will absorb any price increase and continue to buy
the same quantity** (essential goods with a price elasticity of zero), the consumer will pay 100% of the tax.
At the other extreme, when a consumer would not purchase a product if the price increased any further, then the firm absorbs all of the taxation.
This is intuitive - when the buyer will pay any price increase, the firm can pass all of the tax onto the consumer. When consumers are very price sensitive however, the firm will lose a lot of sales if it increases the price - this will cost it a lot of profit.
All possibilities in between can also occur depending upon willingness to pay of the consumer***.
Yes, I know economics doesn’t really tell us who pays how much at all - but it does tell us on what the split depends.
At Terminal 4 of JFK airport in New York, I noticed a nice little experiment to see who pays what.
In only one shop before security (but after baggage check-in) are sales duty free. In all other stores, a sales tax of 8.875% must be added to the price shown on the label (it is not automatically included in the price tag!) See THIS blog entry.
A big 60oz bag of Hershey’s Kisses costs $17.50 in the duty free store. All of that money goes to the store (who then has to pay for all costs). In another store, sales tax must be paid, but it is not shown on the price tag. How much would I expect to pay?
My intuition and the economic theory (which came first, the chicken or the egg?) tell me that the price I will pay in the other store will be above $17.50, but that the amount received by the store will be below that. If the cost is shared equally by me and the store, then I would expect to see a price labeled of $16.77. There would then be a tax of $1.47 on top of that, so that I would have to pay a total of $18.24.
Compared with the price of $17.50, I would pay an extra 74 cents. Compared with the receipt of $17.50, the store would receive 73 cents less (okay, I rounded a little there).

But that is *not what happened*. In the (seemingly mostly chocolate) store, the price label was $15! They receive a whole $2.50 less than the other store. I pay a total of $16.31 – that’s $1.19 less, even after tax!
What has happened here? Surely the sales tax hasn’t acted to decrease the prices?!
I strongly doubt it, but I don’t have any explanations that convince me. Of course, as always in economics, there are a number of assumptions and caveats, so maybe these would be a good place to start to search for an explanation. These assumptions are:
1/ Airport consumers do not ‘shop around’ (as indeed, I did, to some extent) for their purchases and basically choose to buy or not to buy in each store separately - although I think that they should be able to have already seen one price and made one decision, and then seen another price and made a different decision (would probably need a mathematical model to verify for sure that this last statement is logically consistent) - a good dissertation topic for a final year or post-grad student?!
2/ The small price difference means that it is not systematically worth consumers’ time returning the more expensive product and buying the cheaper one instead or that most consumers do not notice both prices.
3/ There are no behavioral responses such as the very fact that I see two prices for the same good encourages me to buy the cheaper one because I feel that I am getting a bargain.
I think that these are mostly reasonable and, in fact, if the first two occurred systematically, then the prices would equalise to end up exactly the same through competition, so this cannot always be happening although the prices may incorporate a bit of all of these.
So I think that these caveats are reasonable. I have only one further explanation: Customers don’t buy just what they walk out of the shop with – they buy a whole shopping experience. I think that the customers that go to a duty-free shop to purchase expensive perfumes, liquors etc. are not the same people who walk into a chocolate shop (present blogger excepted).
The people who go to the duty-free are either (a) prepared to pay more for a more fancy shopping experience or (b) have a different price elasticity to those who go to a chocolate shop – i.e. they don’t mind paying more.
Any other explanations?
* At least over the relevant domain.
** I will ignore supply elasticity for simplicity.
*** And also the willingness to supply ad different prices of the producer but I abstract from that for the moment and assume a simple upward-sloping supply curve.