observations and reports

Signalling games are dynamic games with two players, the sender (S) and the receiver (R). The sender has a certain type, t, which is given by nature. The sender observes his own type while the receiver does not know the type of the sender. Based on his knowledge of his own type, the sender chooses to send a message from a set of possible messages M = {m1, m2, m3,…, mj}. The receiver observes the message but not the type of the sender. Then the receiver chooses an action from a set of feasible actions A = {a1, a2, a3,…., ak}. The two players receive payoffs dependent on the sender’s type, the message chosen by the sender and the action chosen by the receiver [1][2]. A related game is a screening game where rather than choosing an action based on a signal, the receiver gives the sender proposals based on the type of the sender, which the sender has some control over.

Signalling (economics)

In economics, more precisely in contract theory, signalling is the idea that one party (termed the agent) conveys some meaningful information about itself to another party (the principal). For example, in Michael Spence’s job-market signalling model, employees signal the level of their skills to employers by acquiring a certain degree of education.

Contents

• 1 Introductory questions
• 2 A basic job-market signalling model
  • 2.1 Assumptions and groundwork
  • 2.2 The result
• 3 References
• 4 See also

Introductory questions

Signalling took root in the idea of asymmetric information (a deviation from perfect information), which says that in some economic transactions, inequalities in access to information upset the normal market for the exchange of goods and services. In his seminal 1973 article, Michael Spence proposed that two parties could get around the problem of asymmetric information by having one party send a signal that would reveal some piece of relevant information to the other party. That party would then interpret the signal and adjust her purchasing behaviour accordingly — usually by offering a higher price than if she had not received the signal. There are, of course, many problems that these parties would immediately run into.

• How much time, energy, or money should the sender (agent) spend on sending the signal?
• How can the receiver (the principal, who is usually the buyer in the transaction) trust the signal to be an honest declaration of information?
• Assuming there is a signalling equilibrium under which the sender signals honestly and the receiver trusts that information, under what circumstances will that equilibrium break down?

A basic job-market signalling model

In the job market, potential employees seek to sell their services to employers for some wage, or price. Generally, employers are willing to pay higher wages to employ better workers. Since employers are not always able to observe potential employees skills and productivity, they use education as a way to estimate the abilities of potential employees.

Assumptions and groundwork

Spence began his 1973 model with a hypothetical. Suppose that there are two types of employees — good and bad — and that employers are willing to pay a higher wage to the good type than the bad type. Spence assumes that for employers, there’s no real way to tell in advance which employees will be of the good or bad type. Bad employees aren’t really upset about this, because they get a free ride from the hard work of the good employees. But good employees know that they deserve to be paid more for their effort, so they invest in the signal — in this case, some amount of education. Spence assumes that education does not enhance the employee’s productivity at all. But he does make one key assumption: good-type employees pay less for one unit of education than bad-type employees. This is not indicative of the cost of tuition and living expenses, as one would expect better employees to get educated at better and more expensive institutions. Rather, it is indicative of the opportunity cost that is paid by the time and effort invested into obtaining the education, which for a more efficient “good” employee, would be less than for a less efficient “bad” employee getting the same degree with the same grades from the same institution.

The result

Spence discovered that even if education did not contribute anything to an employee’s productivity, good employees would still buy more education in order to signal their higher productivity to employers. This is also called sheepskin effect for the reason that degrees used to be written on sheepskin.(Economists sometimes call this the signalling hypothesis in education, often cited as a reason why government should not subsidize higher education for workers: more education allows workers to be paid a higher wage but does not make society more productive.) Bad workers, for their part, would accept a lower wage rather than pay the higher price (for them) of getting more education. And employers, seeing that the education signal really is correlated to employee productivity, would condition their wages on the signal, offering better wages to those who had invested more in the signal. This is called a signalling equilibrium.

mcgillicuddy: