Tables, percentages and index numbers

Raw data are a jumble of figures, hard to understand. Tables arrange them in rows and columns, so they can be compared easily.

Data can be presented in three forms:

• Absolute data: the original figures as counted, such as the population of each state.
• Percentages and ratios: for example, the literacy rate = literates ÷ population × 100.
• Index numbers: they show change compared with a base (a base year, or a base place), which is taken as 100.

Example of an index number: a state produced 40 lakh tonnes of wheat in the base year, and 50 lakh tonnes ten years later. Taking the base year as 100, the later year's index = 50 ÷ 40 × 100 = 125: production rose by 25 per cent.

Index numbers can compare years, and also places (taking one place as the base).