Age, period, and cohort effects

What is the APC identification problem?

The book Generations by Bobby Duffy (KCL) highlights the import of generational thinking. All changes over time in attitudes, beliefs, and behaviour separate into three effects:

• Age effects: People change as they age, due to biological and social reasons. For example, life events like retirement can affect people. The book refers to these as ‘lifecycle effects’.
• Period effects: The change occurs in a consistent manner across all age groups. These effects are…