Types of index numbers include various classifications. Laspeyres index: uses base year weights (more conservative). Paasche index: uses current year weights (reflects current structure). Fisher ideal index: geometric mean of Laspeyres and Paasche. Key concepts: weight choice affects index behavior. Common traps: confusing Laspeyres (base) vs Paasche (current), calculation errors. Exam tips: remember Laspeyres is more commonly used. Time-saving: identify index type from problem context. Weighted indices: account for quantity importance. Simple index: single item or unweighted average. Complex index: multiple items with weights. Applications: inflation measurement, productivity tracking. Relationships: Paasche typically lower than Laspeyres for price increases. Understanding index types essential for proper application. Practice identifying and calculating each type.