I recently got an iPhone, and I don’t know how I lived without it. For the not-so-brief period of time that I didn’t have Internet at home, it was my lifeline connecting me to my Email and my distant wife. One of the fun things about the iPhone is the App Store. You can browse through and download applications from a collection of thousands of applications. When browsing an application in the App Store, each application displays a distribution of ratings on a scale of one to five stars. This really helps evaluate applications; if lots of people didn’t like it, then I usually won’t download it.
One of the things that really surprised me when I got my iPhone is the large number of ratings. Most applications that I looked at had hundreds or thousands of ratings. That’s as much or more than the number of ratings that products on Amazon.com get. Why would so many people spend their time rating applications they have used?
It turns out that the way most of the ratings are collected is by prompting users for a rating when they delete an application. I guess that Apple figures people will have used an application enough to have an opinion about it if they are deleting it.
This reminded me a lot of an “incentive mechanism” that is well known in the field of Philanthropy: the “Power of the Ask.” (Anderoni, 2006) Basically, when you want someone to give money to your charitable organization, one of the most effective methods is to approach them and ask them to donate. Outright asking works for a couple of reasons: 1) it changes the question from “which charity should I donate to” to “should I donate to this charity.”; this helps the charity doing the asking at the potential expense of other charities. 2) It solves the problem of when to make the donation; people cannot procrastinate or put off donation when being asked to do so now.
Thinking a little deeper, though, the mechanism used by Apple’s App Store is subtly different. The main difference is that Apple is asking for a contribution of information rather than money. All information isn’t the same; there is good information and bad information. Or, more accurately, there is useful information and biased / wrong information. When asking for money, a charity doesn’t have to worry about getting bad money; if they get any money at all it is good. However, Apple needs to worry that people will provide bad information. Asking isn’t enough; you need to somehow ensure that the information is high quality and useful.
I think Apple might have done this wrong. Specifically, they only ask for a rating when a user is deleting an application. So all the unsatisfied users who delete an application rate it low. All the satisfied users who don’t delete it and keep using it never get asked, and never contribute a rating. This means that the overall ratings are biased to be much lower than the community truly thinks they are. This illustrates one reason why “the power of the ask” doesn’t always for in information settings in the way that it does in charity / money settings.
Unfortunately, solving this problem isn’t easy. You could randomly prompt people for ratings, or ask them N days/weeks/months after they install an application, but that would be very annoying for the users. If you don’t ask, then your ratings will be more unbiased, but very few people will contribute.
J. Andreoni. Philanthropy. In S.-C. Kolm and J. M. Ythier, editors, Handbook of Giving, Reciprocity and Altruism, pages 1201–1269. North Holland, Amsterdam, 2006.
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