The vast majority of Internet surveys are conducted using “online” panels (known as access panels, online or opt-in panels). As non-probability samples, access panel surveys have been questioned based on general theoretical arguments and empirical studies. Although convincing, these theoretical arguments cannot rule out the possibility that a specific survey on a specific access panel may produce results that are very close to those of a competing, high-quality probability survey. On the other hand, empirical studies are conducted on a limited set of panels and do not inform on the very nature of panelists in general that explains the biases …