Hierarchical models, or multilevel models, are used to represent data that might vary on, you guessed, different levels. Michael Freeman, from the University of Washington Information School, provides an introduction to the method using a scrolling format. The transitions give a good sense of how the model can change, depending on your approach.
Visual explainer for hierarchical modeling
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Income in Each State, Adjusted for Cost of Living
A dollar might not buy you as much in one state as it does in the other.
Who Makes More Money
Someone mentioned that $400,000+ per year was commonplace in American households. That seemed like an odd comment.