Construction of index numbers involves systematic steps. Step 1: Select items and base year. Step 2: Collect prices (or quantities) for all periods. Step 3: Determine weights (if weighted index). Step 4: Calculate relative (current/base) × 100. Step 5: Apply weights and aggregate. Laspeyres: Σ(p_current × q_base) / Σ(p_base × q_base) × 100. Paasche: Σ(p_current × q_current) / Σ(p_base × q_current) × 100. Common traps: arithmetic errors in aggregation, inconsistent units. Exam tips: organize data in table format, verify calculations. Time-saving: recognize formula structure, calculate step-by-step. Data organization: clear headers, aligned columns, calculated columns. Applications: business indices, economic indicators. Quality checks: compare results with known indices. Understanding construction enables custom index creation. Practice with real economic data.