What is Verifiable Information?

What does it mean to say that a piece of information is verifiable? Verifiable information is a term that is fairly common in the economics literature. For instance, Baird et. al. note that "some information is verifiable; that is, it can be readily checked once it is revealed. For example, the combination to a safe is verifiable information. The combination either opens the safe or it does not. Other information is nonverifiable. An employer wants to know whether a guard who was hired was vigilant. The employer might be able to draw inferences from some events, such as whether a thief was successful or was caught, but such information may not be available and, even if it is available, may not be reliable. Even a lazy guard may catch a thief, and a thief may outwit even the most vigilant guard" (Baird et. al., 1994, p. 89). Basically, a piece of information is verifiable if and only if it is easy to determine whether or not the information is accurate.

This characterization provided by Baird et. al. captures some of the essential aspects of verifiable information. For instance, the verifiability of a piece of information is independent of the accuracy of the information. The claim that 8-11-64 is the combination to the safe is verifiable whether or not that really is the combination. The claim that the guard is vigilant is nonverifiable whether or not the guard really is vigilant. However, there are several important subtleties that are not made explicit in Baird et. al.'s characterization of verifiable information.

First, this characterization suggests that either a piece of information is verifiable or it is not. However, verifiability is something that comes in degrees. In fact, it is a trivial matter to find pieces of information that fall at various different points on the continuum of verifiability. For example, the claim that the safe is gunmetal gray is somewhat easier to verify than is the combination of the safe. Also, the claim that the guard is a descendent of Charlemagne is much harder to verify than is the vigilance of the guard. As a result, we should really speak of the verifiability of information rather than just verifiable versus nonverifiable information.

The verifiability of a piece of information can be measured by how much it costs to determine whether or not the information is accurate. The more time and energy that an Internet user has to expend in order to verify a piece of information, the less verifiable that information is.

This gives us a verifiability scale. Some information can be verified at no cost at all. (This is essentially information that the Internet user already knows to be true.) Some information cannot be verified no matter how much time and energy the Internet user expends. We will say that the cost of verifying such information is infinite. Most information falls somewhere in between on the verifiability scale.

Second, this characterization suggests that the verifiability of a piece of information is static. However, it is often possible to increase (or decrease, for that matter) the verifiability of a piece of information. For example, it becomes much easier to determine whether or not the guard is vigilant if we install a video camera to monitor her. (In fact, increasing the verifiability of a piece of information facilitates the acquisition of knowledge because people are more likely to verify that a piece of information is accurate if it costs them less to do so.)

I should note that increasing the verifiability of a piece of information is not the same as increasing the accuracy of the information. The authors of web pages can (and probably should) employ practices that make it more likely that their information is accurate. For instance, an author might insist on having at least two sources who corroborate anything that she publishes on her web page. Employing such a practice will certainly facilitate the acquisition of knowledge by increasing the percentage of accurate information on the Internet. However, it will not by itself do anything to make it easier for people to determine whether or not the information is accurate.

Finally, this characterization suggests that the verifiability of a piece of information is the same regardless of who is trying to verify it. However, the verifiability of a piece of information depends on the circumstances and capabilities of the individual who is trying to verify it. It will cost you a lot more time and energy to check the combination if the safe is in New York and you are in LA than it would cost you if you were in the same room with the safe. Similarly, it will be much easier for a trained physicist to verify a claim about the behavior of subatomic particles than it will be for a layman to verify the same claim. (Note: The following diagram assumes that the safe is in NY.)

Reference

Baird, Douglas G., Robert H. Gertner, and Randal C. Picker. 1994. "Signaling, Screening, and Nonverifiable Information." Pp. 122-58 in Game Theory and the Law, Cambridge: Harvard University Press.