The document discusses index numbers, which are statistical devices used to measure changes in groups of related variables over time. It provides examples of different types of index numbers, including price indexes, quantity indexes, consumer price indexes, and weighted vs. unweighted indexes. The key methods of calculating index numbers are also examined, such as the Laspeyres and Paasche formulas for weighted price indexes. Index numbers are shown to be important tools for comparing economic indicators over time and informing policymaking.