(If you’re visiting for a new game theory article, I apologize. This week went by really quick and I don’t have a new article to post. In the meantime do browse the game theory archive…Thanks and see ya next week).
In 1994, shock jock Howard Stern created a public storm and ran for the governor of New York. His campaign was regarded as a publicity stunt, but some worried his radio popularity would convert into votes and make a mockery of American politics. Luckily, the fears never materialized. Stern dropped out because he didn’t want to disclose his finances (or salary), a requirement for office.
The story illustrates an interesting part of American culture: most of us treat salary as personal information. Like Stern, we worry about things like being judged by peers or getting charged more by unscrupulous mechanics and plumbers.
But that’s only half of the story. We occasionally find ourselves on the other side of the table when we’re looking for jobs and we need to learn about salaries. In this case, we have to be careful to learn about salary information without coming off as nosy or rude.
So we’re left with a daunting challenge: How can we learn about salaries without asking too much personal information?
This is a question that requires some strategic thinking. If you’ve been reading this blog, you know that game theory and strategy are often best illustrated through puzzles. In the past I’ve used puzzles to explain fixed points (the monk puzzle), group coordination (the hat puzzle), Monte Carlo simulation (the dice puzzle), ESPN’s million dollar streak contest (the tennis puzzle), survival of the weakest (the truel) and even the Joker’s motivation in the Dark Knight (the pirate puzzle).
The game of salary information too can be understood better through today’s puzzle.
The salary puzzle
Three friends want to know their average salary for negotiating purposes. How can they do it without disclosing their own salaries to each other?
A hint to get started: read the article on email encryption
The answer (will be posted next week)
(Wow, thanks for all the comments while I was posting this. Scott, Dan and Ku were all thinking along the right lines and Cheryl offers a practical and direct way I didn’t even think about)
The friends can calculate the average through a clever encoding process. The idea is that each person encodes their salary by adding a random number to it. These encoded salaries can be added together and then the random numbers can be subtracted. The resulting figure is the sum of the three salaries from which the average can be obtained.
Since additions and subtractions are easy to decode, however, the tricky part is implementing a solution where no person obtains knowledge of the other two party’s random numbers, for that would reveal enough information to obtain individual salaries. To do that, one can sequence the additions and subtractions carefully.
The process is somewhat cumbersome, but its gets the job done. Here is one particular solution, with the supporting algebra as verification:

Here is a worked out example with specific values:

Strategic considerations
The solution is interesting but it begs for further analysis. There are several considerations that came to mind which are addressed below.
Can the solution be extended for more than three players?
Yes. The process can scale up, but there are a few practical problems. First, it might be hard to coordinate a larger group. Second, there is a risk that the average may get “diluted” by incorporating workers of different skill levels. Third, adding more people will likely increase the chance of lying players and collusive groups. These turn out to be tremendous problems.
What happens when someone lies?
Alas, the answer to the salary puzzle is too idealistic. It depends entirely on individuals telling the truth. In fact, from a strategy perspective, it makes a lot of sense to lie.
Why lie? It’s important to consider your action relative to what others do. If others tell the truth, then the algorithm will produce a result equal to the sum of their true salaries plus the number you report. With this information, you can still compute the group average because you know your own salary. You might as well lie since honest reporting provides no benefit but comes at the risk of others learning your salary.
If, on the other hand, someone else has lied, then you definitely don’t want to be honest in reporting your salary. You have no chance of finding the correct average, and honest reporting has the risk of your salary getting disclosed.
Here’s an example of how someone lying can take advantage of the game:

How might the game play out if people thought strategically? (What is the Nash equilibrium of the game?)
As discussed above, lying is a dominant strategy. If others are honest, it makes sense to lie since you get the same benefit without any risk. And if others lie, you have nothing to gain and honesty comes with a risk. Therefore, everyone lies and the average is meaningless.
What would happen if players collude?
Another flaw to the salary puzzle is that it’s susceptible to collusion. If a few players decide to cooperate in advance, they can con the other members of the group.
To see how, suppose players B and C simply want to learn player A’s salary. They can do this by lying and sharing their fake numbers with each other, as follows:

Final remarks: how to share salaries in practice
As this puzzle illustrates, there are many strategic reasons why it can be hard to learn salary information. People are scared of revealing information without getting anything in return, exactly because it’s easy and favorable to lie.
How can we get around this problem? First, players should be guaranteed some useful information so they want to participate. Second, players need to be given a reason to be honest, or else they will free ride on other people’s honesty. And finally, the process should be anonymous so that no one fears revealing their personal salary information to others face to face.
Amazingly, it seems there are websites coming up that deal with these issues. One that I recently came across is glassdoor.com which allows you to look at salaries for job titles after you provide a salary for a current or previous employer. I haven’t had a chance to use the site myself, but it sure seems interesting.
I’m curious has anyone tried it out? Any other sites like this?