Index Number — Formula Sheet

Price Relative = (p₁ / p₀) × 100

Index Number (simple) = Σ(p₁/p₀) / n × 100

Fixed Base Index = (Value in current year / Value in base year) × 100

Chain Base Index (CBS) = (Value in current year / Value in preceding year) × 100

FBS → CBS: CBS = (Current year FBS / Previous year FBS) × 100

Price relative of an item = (Current year price / Base year price) × 100

BASE YEAR

A normal, stable year free from unusual events (flood, drought, war, strike, pandemic) used as a reference. Index value of base year = 100.

CONVERSION FORMULA (Fixed → Chain)

CBI of current year = (FBI of current year / FBI of previous year) × 100

CONVERSION FORMULA (Chain → Fixed)

FBI of current year = (CBI of current year × FBI of previous year) / 100

Index Number = (p₁/p₀) × 100; base year value is always taken as 100

Fixed Base

All years compared to ONE fixed year. FBI = (Current/Base Year) × 100

Chain Base

Each year compared to PREVIOUS year. CBI = (Current/Previous) × 100