What are weights?
Most MPC datasets are samples of a population; each sample case represents anywhere from 20 to 1000 people in the complete population for the given year. The “weight” variables indicate how many persons in the population are represented by each sample case. Some samples are unweighted or “flat”, meaning that every person in the sample data represents the same number of persons in the population. But most samples are “weighted”, meaning that some sample cases represent more people in the population than others. Persons and households with some characteristics are over-represented in the samples, while others are underrepresented. Weight variables allow researchers to create accurate population estimates using weighted samples.