To judge whether price increases are sustainable, the key is price testing. Because price is such a potent weapon of value creation or destruction, price testing should be an ongoing practice at firms, but it's not. There is surprising inertia at companies when it comes to price testing and an over-reliance on surveys. Surveys are by far the most common way that companies try to get some sense of their customers' price elasticity or inelasticity. There are a couple of problems with surveys when it comes to making pricing decisions. One thing we know for certain from market research is that there is very often a difference between what people say in surveys and their actual marketplace behavior. A classic example is surveys about products in many environmental or green categories. A high percentage of respondents are [for the green option] in the survey, but then in their marketplace behavior, they will trade that option for convenience or a lower price. So the first big problem is what people say versus what they do. This is an instance of what economists call revealed versus stated preference. But online technologies have made it increasingly viable for companies in most industries to do A/B testing and other tests in which you have the same product at two different prices in different distribution channels or different online media. And there, you're testing not what people say in a survey but their actual behavior. They either click or they don't click, they either move to the next stage or they don't move to the next.