The term "middle class" is frequently referenced, yet the exact meaning is often unclear. As this August 2020 data visualization essay from The Pudding highlights, "for many people, the 'middle class' is just as much about your education, job, resources, and aspirations as it is about your paycheck." To better understand this socioeconomic metric, this story tracks 11,172 families from the years 1968 to 2018. All of these families "spent at least one year in the middle class." However, their specific economic position changed over this time period. This concept of "mov[ing] between income quintiles," is known as economic mobility. Just how much did families' economic positions change over time? Most "move[d] at least one quintile during their lifetimes, with nearly half moving two quintiles." Interactive charts throughout the project explore other aspects of income mobility, including racial disparities. Overall, the project illuminates the importance of examining income changes over time to see a "more nuanced picture of how the middle class is doing," and understand how "economic conditions" shift over one's lifetime. The data used in this story comes from the University of Michigan's Panel Survey on Income Dynamics (PSID), and more information on the data analysis process is available in the Methods section at the end of the piece.