Measurement Methods for cycles involve quantifying fluctuations and extracting cycles from data. GDP measurement: Nominal GDP (current prices), Real GDP (constant prices), adjusted for inflation. Growth rate calculation: (GDP_t - GDP_t-1)/GDP_t-1; can be annualized, quarterly, or year-over-year. Index numbers: Typically scaled to base year = 100; facilitates comparison across time. Detrending: Removing long-term trend to isolate cycle; methods include moving averages, trend lines, statistical techniques. Deviations from trend: Cycle measured as percentage deviation of actual from trend. Hodrick-Prescott filter: Statistical method separating trend from cycle; widely used in academia. Band-pass filter: Alternative method emphasizing specific frequency ranges. Seasonality adjustment: Removing seasonal patterns (e.g., Q4 typically higher due to holidays) to see underlying trend. Smoothing: Averaging across periods to reduce noise and reveal underlying patterns. Concordance index: Measures co-movement between series (if rising together). Industrial production index: Measures manufacturing, mining, utilities output; leading indicator. Purchasing Managers' Index (PMI): Business survey index; earlier indicator than official GDP. ICAI focus: Data sources, detrending methods, commonly used indices. Exam tip: Seasonal adjustment important (don't confuse seasonal spikes with real expansion); distinguish trend from cycle in analysis.