View source for Price discrimination

{{pricing strategy}}

==Definition==

===Definition for a single seller and a single good===

'''Price discrimination''' is the following [[pricing strategy]] used by a ''single'' [[defining ingredient::seller]]: selling identical [[defining ingredient::good]]s (identical in terms of production costs) at different [[defining ingredient::price]]s to different [[defining ingredient::buyer]]s.

===Definition for a single seller and multiple goods===

This more general (and somewhat different) definition is due to George Stigler ([[Book:TheoryofPriceStigler|''Theory of Price'', 1987]]): price discrimination is present when two or more goods are sold at prices that are in different ratios to marginal costs.

===Relation to the law of one price===

Price discrimination is counter to the [[law of one price]] and is related to the phenomenon of [[price dispersion]]. Price discrimination refers to a single seller selling the same good at different prices, while price dispersion refers to the spread in prices of identical goods across the market, usually across multiple sellers.

==Motivation behind price discrimination==

===Price discrimination practiced for profit===

Price discrimination is profitable in situations where different consumers have different demand curves for the same product. Here is a simple illustrative example that assumes a single yes/no decision for purchase rather than a decision on volume. This example illustrates [[first-degree price discrimination]].

Suppose a seller produces a good at a price of <math>x</math> money units per piece, and there is no competition. Buyer <math>A</math> is willing to pay a maximum of <math>y</math> units for the good, and buyer <math>B</math> is willing to pay <math>z</math> units for the good. In other words, the [[reservation price]]s of buyers <math>A</math> and <math>B</math> are <math>y</math> and <math>z</math> units respectively. 

We first consider the case where <math>\! z > y > x</math> and <math>\! z - x > 2(y - x)</math>. For instance <math>\! x = 5, y = 10, z = 30</math>.

{| class="sortable" border="1"
! Situation !! How the seller acts and buyers respond !! Producer surplus !! Consumer surplus !! Social surplus 
|-
| Single price chosen by seller for all buyers (no price discrimination) || Seller prices good at <math>z</math>, <math>B</math> buys, <math>A</math> doesn't. || <math>\! z - x</math> || <math>\! 0</math> || <math> \! z - x</math>
|-
| Separate price for each buyer || Seller prices at <math>y</math> for <math>A</math> and <math>z</math> for <math>B</math>, both buy. || <math>\! y + z - 2x</math> || <math>\! 0</math> || <math>\! y + z - 2x</math>
|-
| Perfectly competitive market with a market price of <math>w > x</math> || seller prices at <math>w</math> units, both <math>A</math> and <math>B</math> buy || <math>\! 2(x - w)</math> || <math>\! y + z - 2w</math> || <math>\! y + z - 2x</math>
|}

Note that in practice, the surpluses listed as zero will be slightly greater than zero, because of some lack of perfectness in information and competition.

We next consider the case where <math>\! z > y > x</math> and <math>\! z - x < 2(y - x)</math>. A numerical example would be <math>\! x = 5, y = 10, z = 12</math>.

{| class="sortable" border="1"
! Situation !! How the seller acts and buyers respond !! Producer surplus !! Consumer surplus !! Social surplus
|-
| Single price chosen by seller for all buyers (no price discrimination) || Seller prices good at <math>y</math>, <math>A</math> and <math>B</math> buy. || <math>\! 2(y - x)</math> || <math>\! z - y</math> || <math>\! y + z - 2x</math>
|-
| Separate price for each buyer || Seller prices at <math>y</math> for <math>A</math> and <math>z</math> for <math>B</math>, both buy. || <math>\! y + z - 2x</math> || <math>\! 0</math> || <math>\! y + z - 2x</math>
|-
| Perfectly competitive market with a market price of <math>w > x</math> || seller prices at <math>w</math> units, both <math>A</math> and <math>B</math> buy || <math>\! 2(x - w)</math> || <math>\! y + z - 2w</math> || <math>\! y + z - 2x</math>
|}

In both cases, we see that the seller benefits from price discrimination. In the first case, the benefit is through the expansion of the market to buyer <math>A</math>. In the second case, the seller benefits by being able to charge <math>B</math> more rather than being forced to charge <math>B</math> the same as <math>A</math>.

Note that although the term ''profit'' is used here, price discrimination may well be practiced in the same manner by institutions or firms that are not ''profit-making'', including governmental institutions and private nonprofits.

===Price discrimination practiced for non-economic reasons===

Price discrimination may be practiced by governmental or private firms for ''social goals'' or for ''taste-based reasons''.

==Conditions for price discrimination==

The main problem with price discrimination strategies is the ''leakage'' of the low-price product to customers who might have been willing to pay the higher price. The conditions are summarized in a table and detailed further below.

{| class="wikitable" border="1"
! Condition !! Why it is necessary
|-
| Difference among buyers in willingness/ability to pay || Otherwise, there is no basis/criterion along which the seller should price discriminate
|-
| Market power for the seller || In a perfectly competitive market, price discrimination is undercut as competitors offer lower prices to the customers paying the highest prices under a price discrimination system.
|-
| Preventing high-priced customers from choosing low-priced alternatives || This is necessary to make the charging of different prices to different customers effective.
|-
| Difficult to resell || If the low-priced versions are easy to resell, it is more difficult to maintain the high prices.
|}

===Differences in willingness/ability to pay===

Different buyers need to be different in some meaningful way for price discrimination to make sense. This difference may be in the following ways:

* Differences in the buyers' [[reservation price]]. This may, in turn, be caused by different degrees of (perceived) private benefit they receive, or due to [[wealth effect]]s or [[income effect]]s. Note that such differences can exist even in markets with perfect information and zero transaction costs.
* Difference in the awareness of buyers about alternatives. Different buyers with the same reservation price may effectively be willing to pay different amounts because of different degrees of awareness of alternatives.
* Difference in the [[transaction cost]]s imposed on buyers either for that product or for alternatives, which affects their effective reservation prices.

===Market power===

{{further|[[Price discrimination requires market power]]}}

For a seller to practice price discrimination, i.e., to price the same good differently to different buyers, the seller must have at least some [[market power]]. For instance, if a seller has both a ''low price'' for some buyers and a ''high price'' for other buyers, another seller can come along and offer the same good at a medium price for all buyers. The other seller is thus able to steal the most profitable customers from the original seller, forcing the original seller to lower prices. In this manner, a competitive market erodes price discrimination.

===Preventing high-price buyers from choosing low-price alternatives===

Price discrimination requires strategies to prevent customers in the high-price segment form choosing the low-price version. The strategies are of many kinds:

* Requiring certain eligibility conditions to qualify for the low-price product. The eligibility criteria may include geographic location (lower prices in developing and backward areas), time, or demographic characteristics of the buyer (for instance, student discount cards, senior citizen discount cards, clipper coupons).
* Requiring customers to put in extra work to obtain the low-price product: This includes methods for arranging items in supermarkets so that price-insensitive customers are likely to pick the high-price versions while bargain shoppers are likely to pick the low-price versions.
* Deliberately sabotaging low-price products at added cost to prevent people willing to pay a higher price from switching to the lower price: This is observed in knowledge goods. {{further|[[Price discrimination for knowledge goods]]}}
* Using marketing techniques to make high price payers believe that the high-price product is different or superior.

===Difficult to resell===

{{further|[[price discrimination requires difficulty of resale]]}}

If it is easy for people to ''resell'' goods obtained at the low price to buyers willing to pay the higher price, price discrimination is difficult to maintain.

==Alternative explanations for apparent price discrimination==

If price discrimination seems to be occurring, but the conditions necessary for successful price discrimination are not satisfied, there are likely to be alternative explanations. Alternative explanations to price discrimination usually hinge on [[hidden cost]]s, such as [[opportunity cost]]s, greater expectations of customers paying higher prices, and non-obvious differences in quality. Here are some examples:

* Greater price as a proxy for costs of time, space, or other options that are not directly charged for: For instance, in restaurants, food and drink items that are typically ordered by customers seeking to stay for long may be charged higher, to compensate for the time spent occupying the table.
* Greater price for clients who are likely to be more demanding: Buyers who are more likely to demand better goods and service, or place other additional demands on the sellers, may be charged more to compensate.

==Models of behavior and organization for price discrimination==

===In perfectly competitive markets with completely rational behavior and no transaction costs===

Price discrimination has no place in perfectly competitive markets where transaction costs are zero and everybody has perfect information and is rational.

===In non-competitive markets===

In a market where some sellers have market power, the conditions for price discrimination (difficult to resell, easy to prevent leakage of low-price versions to high-price buyers) may exist even with completely rational behavior, zero transaction costs and perfect information.

For the extreme case of a monopoly, see [[determination of price and quantity supplied by price-discriminating monopolistic firm in the short run]].

===With variable transaction costs and variable degrees of imperfect information===

In a perfectly competitive market where all players behave rationally, price discrimination may still exist if different buyers have different [[transaction cost]]s or different degrees of information, leading to a difference in the prices they are effectively willing to pay. In fact, such a difference may emerge even with very similar [[reservation price]]s, and it may even act in a direction opposite to reservation prices. (Thus, rich buyers may also be better informed about alternatives and may thus get ''lower'' prices for goods even though their reservation prices may be higher).

However, if the market is sufficiently competitive, these differences tend to remain small, because competing sellers, in conjunction with smart buyers who put pressure on them, help spread information about the cheaper versions even to individual buyers who do not have enough information.

===With irrational behavior===

Even in the presence of low transaction costs, the complete availability of information, and perfectly competitive markets, irrational behavior on the part of buyers could lead to small amounts of price discrimination. These amounts must, however, remain small because competitors to a seller practicing significant price discrimination can raise awareness of the issue.

In practice, we see price discrimination practiced in situations where there is a reasonable degree of market power (though far from a monopoly), non-negligible transaction costs and lack of perfect information, and further, the techniques used for price discrimination typically try to exploit systemic behavioral biases.

==Types of price discrimination==

The classification of price discrimination discussed here is that outlined in [[Book:EconomicsofWelfarePigou|Pigou's book]].

===First-degree price discrimination===

{{further|[[First-degree price discrimination]]}}

First-degree price discrimination, also called '''perfect price discrimination''' is a form of ''individual targeting''. It describes a situation where a seller can charge different prices to different consumers, based on whatever price the seller thinks is best for each consumer. Here, the seller uses various methods to try to determine the [[reservation price]] of each consumer (reservation price is the maximum price the consumer is willing to pay) and charge close to that. Thus, the seller can milk the maximum profit from each consumer without ever losing a buyer because of high prices. First-degree price discrimination has huge costs both in terms of the cost needed to gather enough information about buyers to guess reservation prices well, and in terms of the added costs when buyers catch on to the strategy and put moral pressure on the seller or otherwise try to fool the seller.

If the costs of discerning reservation prices are zero, first-degree price discrimination is efficient, maximizes [[social surplus]] (at least in the short run), and avoids [[deadweight loss]]. However, all the social surplus is captured by the seller, which is the opposite of the situation in [[perfect competition]], which is efficient and where the social surplus is captured either by consumers or by producers who are more efficient than other producers.

First-degree price discrimination includes the related practice of [[bargaining as price discrimination|bargaining or haggling]].

===Second-degree price discrimination===

{{further|[[Second-degree price discrimination]]}}

Second-degree price discrimination, also called '''nonlinear pricing''' or '''volume-based price discrimination''', describes a situation where the cost per unit is lower the greater the volume a buyer buys. Such price discrimination is useful if it is true that people who are willing to buy larger quantities are also the people who are less likely to be willing to pay higher unit prices. This is usually the case, since consumers buying larger quantities may well be more likely to search for better deals or cheaper alternatives, since more money is at stake. Alternatively, such price discrimination may be explained by the fact that the marginal utility of purchasing additional units of the product is decreasing. Hence, for a given buyer, the reservation price per unit for purchasing a larger quantity is lower.

===Third-degree price discrimination===

{{further|[[Third-degree price discrimination]]}}

Third-degree price discrimination uses ''group targeting''. Here, prices are set at different levels based on region, demographic group, and other factors. Group targeting thus tries to exploit the different demand curves for different demographic groups. Such price discrimination may again be of two kinds: [[direct segmentation]], where the segmentation is based on rules (such as age and geographic location) and [[indirect segmentation]], which more covertly tries to attract high-paying customers to high-priced versions and low-paying customers to low-priced versions.

==Costs and benefits of price discrimination==

Price discrimination indicates the existence of sellers with [[market power]], and this is bad news because sellers with market power may set prices and quantities to maximize their own surplus in a way that does not maximize the social surplus. However, the price discrimination ''itself'' may well be better than the other options for a seller with market power.

===Price discrimination imposes costs of gathering information about reservation prices===

Price discrimination imposes costs on sellers, since they need to determine the reservation prices of a larger number of buyers. These costs are highest for [[first-degree price discrimination]], where the reservation price has to be determined for every individual potential buyer. For [[second-degree price discrimination]] and [[third-degree price discrimination]], the costs are less.

===Price discrimination is good when it expands available markets===

{{further|[[Price discrimination is efficient when expanding available markets]]}}

Consider the example discussed earlier: a seller can produce a good at <math>x</math> units per piece, and there are two buyers, each of whom has to decide whether to buy the good or not, and their reservation prices are <math>y</math> and <math>z</math> respectively, with <math>z > y > x</math> and <math>z - x > 2(y - x)</math>.

{| class="sortable" border="1"
! Situation !! How the seller acts and buyers respond !! Producer surplus !! Consumer surplus !! Social surplus 
|-
| Single price chosen by seller for all buyers (no price discrimination) || Seller prices good at <math>z</math>, <math>B</math> buys, <math>A</math> doesn't. || <math>\! z - x</math> || <math>\! 0</math> || <math> \! z - x</math>
|-
| Separate price for each buyer || Seller prices at <math>y</math> for <math>A</math> and <math>z</math> for <math>B</math>, both buy. || <math>\! y + z - 2x</math> || <math>\! 0</math> || <math>\! y + z - 2x</math>
|-
| Perfectly competitive market || seller prices at <math>x</math> units, both <math>A</math> and <math>B</math> buy || <math>\! 0</math> || <math>\! y + z - 2x</math> || <math>\! y + z - 2x</math>
|}

Thus, price discrimination increases the total social surplus generated. In this situation, price discrimination is preferable for society to the alternative ''single high price''. Nonetheless, it is not preferable to a situation of [[perfect competition]]. Perfect competition not only maximizes social surplus but also gives consumers a larger fraction of it.

===Price discrimination is inefficient when it redistributes resources among existing buyers===

{{further|[[Price discrimination is inefficient when distributing limited resources]]}}

Price discrimination can be bad when it distributes ''limited'' resources from people who value them more (indicated by a willingness to pay more) to people who value them less. Examples are discounts for certain groups for seats in flights and trains. Such discounts may end up allowing people who derive relatively less benefit from traveling to travel in place of others who may have benefited more.

==Psychology==

There are two problems that price discriminators need to overcome in terms of the cognitive/moral/behavioral intuitions and biases of buyers and third parties who might interfere.

* ''Perceptions of unfairness'': Price discrimination may be viewed as unfair since it violates the moral pricinple of treating all buyers equally. Note that such perceptions of unfairness may be a problem not just with the buyers of the specific goods but also with other third parties who may be buying other goods or interacting with the seller in other ways.
* ''Envy'': Somebody who bought the good at the higher price may feel envious and resentful of somebody else who bought the good at the lower price.

Price discriminators use other moral dispositions and biases of people to overcome these two related problems.

===Using a reference price greater than the maximum price===

Generally, the price discriminator sets the list price or reference price as the maximum among the prices charged to all buyers, or sometimes as a price even higher than that. Customers being sold lower prices are then offered discounts through various schemes of [[discounting]] that are designed so as to be made less visible to those who are being sold higher prices.

The advantage of this approach is that by the [[reference price]] effect, all customers feel they are getting a good deal (since they are comparing the actual price they pay to the reference price) and that they have ''saved'' money. This potentially makes them less resentful of others who have ''saved'' even larger sums of money.

The disadvantage is that since the reference price is the price that people look at first, people may initially decide not to purchase the good or service even though they would purchase it at the discounted price. The seller thus needs to make sure that even though the reference price is prominent, people are aware that the actual price will be less.

===Conflating willingness to pay and ability to pay===

Although fairness in the sense of charging the same price to everybody is one moral instinct, another moral instinct shared by many is that people who cannot afford to pay the market price for things that are necessary or highly desirable should be offered these goods at lower prices. This instinct can be exploited by price discriminators.

The goal of profit-maximizing price discriminators is to charge lower prices to people with a lower ''willingness'' to pay (which may include both poor people and rich price-sensitive people). In general, there is a significant relationship between the ''willingness'' to pay and the ''ability'' to pay. Thus, a price discriminator can price discriminate ostensibly on the basis of ''ability'' or ''need'' and thus win moral and social approval even from those who are paying the higher prices. Price discriminators may choose to discriminate purely based on ability rather than on more precise indicators of willingness both because ability is easier to measure and because it generates more moral and social approval.

Another advantage of this is that people paying higher prices feel less resentful of it since they can take pride in the fact they do not ''need'' the lower-priced goods because they are richer or more successful. Thus, the ability to buy the higher priced good becomes a signal of wealth (or of a lack of poverty) and it could possibly be viewed as [[conspicuous consumption]].

===Hiding lower prices from the high price buyers===

Sellers also use a variety of ways to hide lower prices from buyers who are being charged the higher prices. Lower prices may be advertised only in venues where high price buyers are unlikely to find them.

===Making people earn lower prices===

Yet another trick to making lower prices palatable emotionally to higher price buyers is to make it appear that those paying the lower prices have ''earned'' these prices, either through collecting coupons or by coming to the shop at specific hours. Note that perceptions are not the only reason why coupons or [[periodic discounting]] are used -- the main reason is the actual costs imposed that discourages price-insensitive customers from using these options. The emotional aspect of making people feel that the lower priced buyers have ''earned'' the lower prices through their efforts is an added bonus.
==The political economy of price discrimination==

===Influence by market actors on politicians to convince them of price discrimination===

Some market actors try to convince politicians that their competitors are practicing price discrimination. One self-interested motivation for doing this is if the competitors are in fact providing lower prices to certain segments of the market. In some of these cases, the real price discrimination story may be altogether opposite.

Let us say there are two buyers <math>A</math> and <math>B</math> and two sellers <math>C</math> and <math>D</math>. Let us say that for seller <math>C</math> the cost of serving buyer <math>A</math> is <math>2</math> units and the cost of serving buyer <math>B</math> is <math>6</math> units. For seller <math>D</math>, the cost of serving buyer <math>A</math> is <math>1</math> unit and the cost of serving buyer <math>B</math> is <math>5</math> units. In a tabular form:

{| class="sortable" border="1"
! !! Buyer <math>A</math> !! Buyer <math>B</math> 
|-
| Seller <math>C</math>'s cost of serving the buyer || 2 || 6
|-
| Seller <math>D</math>'s cost of serving the buyer || 1 || 5
|}

Let us say further that seller <math>C</math> is charging both buyers <math>5</math> units. In this case, seller <math>C</math> is engaging in a cross-subsidy -- subsidizing buyer <math>B</math> using a large margin from buyer <math>A</math>. Such a cross-subsidy can be viewed as price discrimination, under the more general definition of Stigler.

Suppose seller <math>D</math> chooses to sell to <math>A</math> at <math>1.1</math> units and to <math>B</math> at <math>5.5</math> units. Note that <math>D</math> is not price-discriminating in any sense of the word, since <math>D</math> is setting the price in the same proportion to the cost of production for both buyers. In a tabular form, the prices are:

{| class="sortable" border="1"
! !! Buyer <math>A</math> !! Buyer <math>B</math> 
|-
| Price charged by seller <math>C</math> to the buyer || 5 || 5
|-
| Price charged by seller <math>D</math> to the buyer || 1.1 || 5.5
|}

The combined data in a tabular form:

{| class="sortable" border="1"
! !! Buyer <math>A</math> !! Buyer <math>B</math> !! Charging different prices to <math>A</math> and <math>B</math> (naive and incorrect definition of price discrimination)? !! Charging prices at different proportions to marginal costs (Stigler's sense of price discrimination)?
|-
| Seller <math>C</math>'s (cost of serving, price charged) || (2,5), so price:cost ratio is 2.5 || (6,5), so price:cost ratio is 5/6 (i.e., loss) || No || Yes (different price:cost ratios)
|-
| Seller <math>D</math>'s (cost of serving, price charged) || (1,1.1), so price:cost ratio is 1.1 || (5,5.5), so price:cost ratio is 1.1 || Yes || No (same price:cost ratio)
|}

However, the net result is that <math>D</math> is charging <math>B</math> a little more than <math>C</math> is, and charging <math>A</math> a lot less. Also note that since <math>C</math>'s production costs for '''both''' kinds of customers are higher than <math>D</math>'s prices charged, <math>C</math> cannot change its prices to become more competitive.

However, <math>C</math> can try to convince politicians to crack down on <math>D</math> and force <math>D</math> to offer uniform prices, despite the difference in costs of serving the two kinds of customers, and ''also'' to serve both kinds of customers.

Accusations of price discrimination are often made along with accusations of [[predatory pricing]] (lowering prices below production cost to drive out competitors and achieve market control) and other anti-competitive practices.

===Confusion and conflation===

Often, sellers are accused of using price discrimination for non-economic reasons, such as tastes for certain kinds of buyers, and this is considered unfair and worth acting against. The confusion/conflation could happen in many ways:

* Confusing something that isn't price discrimination for price discrimination, because of the end result that prices are different for different customers.
* Not appreciating the conceptual distinction between profit-based price discrimination and price discrimination for other reasons.
* Confusing price discrimination that is, in a specific instance, profit-based, with price discrimination practiced for taste-based reasons.

Alternatively, even without confusing these many issues, it may be argued that even if price discrimination is not discriminatory in intent and is purely profit-based, it is still immoral because of its greater impact (in terms of prices) on some individuals/groups compared to others, and hence must be forbidden or critiqued.

==Legal regulation of this strategy==

===In the United States===

Price discrimination in sales to retailers, when intended to reduce competition among retailers, is regulated under the [[Robinson-Patman Act]] in the United States. ''Direct-to-consumer'' price discrimination is not illegal.

==References==

===Online encyclopedia/dictionary references===

* [[Wikipedia:Price discrimination|Price discrimination on Wikipedia]]
* [[cee:Antitrust|The entry on antitrust in the Concise Encyclopedia of Economics]]

===Weblog entries/articles===

* {{econlibsearch|"price+discrimination"}}
* {{marginalrevolutionsearch|"price+discrimination"}}

===Journal references===

* {{paperlink|TellisPricing}}

===General-purpose economics textbook references===

These are texts intended for use in undergraduate/graduate economics teaching.

{| class="sortable" border="1"
! Book !! Pages !! Chapter/section !! More comments !! Link
|-
| {{booklink|LandsburgPriceTheory}} || 329-334 || Section 9.3 (''Price discrimination'') || || [http://books.google.com/books?id=dSAebgMIoNIC&pg=PA330 Google Books] (330 onward; 329 unavailable for viewing)
|-
| {{booklink|MankiwPrinciples}} || 326-332 || || || [http://books.google.com/books?id=oRgQ2goeFzwC&pg=PA326 Google Books]
|-
| {{booklink|KrugmanWellsEconomics}} || 376-382 || Chapter 14 (''Monopoly'') || || [http://books.google.com/books?id=zWkhS7GPYlYC&pg=PA376 Google Books]
|-
| {{booklink|HirshleiferGlazerPriceTheory}} || 238-243 || Section 8.4 (''Monopolistic price discrimination'') || || [http://books.google.com/books?id=VbrKgDK-rioC&pg=PA238 Google Books]
|}

===Other textbook references===

{| class="sortable" border="1"
! Book !! Pages !! Chapter/section !! More comments !! Link
|-
| {{booklink|EconomicsofPriceDiscrimination}} || whole book || || ||
|-
| {{booklink|TheoryofPriceStigler}} || 72-?, 210 || || ||
|-
| {{booklink|EconomicsofWelfarePigou}} ||275-289 || Chapter 17 (''Discrimination Monopoly'') || || [http://books.google.com/books?id=i5VrbGqUV6EC&pg=PA275 Google Books]
|-
| {{booklink|HandbookofIndustrialOrganization}} || || Chapter 10 (''Price discrimination'') by Hal Varian || ||
|-
| {{booklink|RothbardMES}} || 739-745 || ''Multiform prices and monopoly'' || The term ''price discrimination'' only appears on Page 745 || [http://books.google.com/books?id=YGi5EbO32hgC&pg=PA739 Google Books]
|}
===Expository book references===

{| class="sortable" border="1"
! Book !! Pages !! Chapter/section !! More comments !! Link
|-
| {{booklink|ArmchairEconomist}} || 157-167 || Chapter 16 (''Why popcorn costs more at the movies and why the obvious answer is wrong'') || || [http://books.google.com/books?id=pWS5zrF_Fz0C&pg=PA157 Google Books]
|-
| {{booklink|UndercoverEconomist}} || 29-55 || Chapter 2 (''What supermarkets don't want you to know'') || || [http://books.google.com/books?id=YAA8hPloNRcC&pg=PA29 Google Books]
|-
| {{booklink|Freedomnomics}} || 22-32 || || || [http://books.google.com/books?id=4JLPkjRUvM4C&pg=PA22 Google Books]
|-
| {{booklink|NakedEconomics}} || 19-20 || Chapter 1 (''The Power of Markets: Who Feeds Paris?'') || || [http://books.google.com/books?id=TYuRuI_VKxMC&pg=PA19 Google Books]
|-
| {{booklink|EconomicNaturalist}} || 41, 84, 153 || || || [http://books.google.com/books?id=1nGy0qL6Yp8C&pg=PA41 Google Books]
|}