Research is critical to assess the prevalence, origins, and consequences of ageism as well as the potential effectiveness of various interventions to fight ageism. A major challenge associated with the assessment of ageism is the fact that being seen as ageist is generally considered to be negative. Most people do not wish to be seen as ageist (Cherry et al. 2015) and so will respond to questions about ageism with caution. Moreover, ageism is highly prevalent and often unnoticed, because it is so ingrained in our lives (Perdue and Gurtman 1990). This is why implicit measures of ageism are recommended to supplement explicit measures (Shiovitz-Ezra et al. 2016). Another challenge associated with the assessment of ageism concerns its subjective nature (Ayalon 2016; Voss et al. 2017). In order to acknowledge an event as ageist, one has to notice the event, interpret it as ageist, and then cite ageism as the cause of the event. Any of these three processes can impact one's willingness to acknowledge ageism. The social context plays an important role, as society clearly defines events as ageist or non-ageist based on current norms and expectations. For instance, whereas asking a job applicant his or her age is the norm in some countries, in other countries asking such a question is not considered acceptable. Hence, the subjective nature of ageism should be acknowledged (Ayalon 2016; Kornadt et al. 2015). In the first chapter of this section (2018; Chap. 25), Snellman argues that most research on ageism to date has focused on empirical data. Less attention has been paid to aspects such as the normative value applied to ageism and theoretical or