Un-weighted Index Numbers, Properties, Types

Un-weighted index numbers are simple index numbers where all items are assigned equal importance or weight, regardless of their actual significance or contribution. These index numbers measure relative changes in prices or quantities without considering the quantity consumed or produced. The Simple Aggregative Method and Simple Average of Price Relatives are commonly used techniques. Though easy to compute and understand, un-weighted index numbers may not accurately reflect real economic scenarios because they ignore the actual impact of each item. Therefore, they are mainly used for illustrative or preliminary analysis rather than precise economic measurement.

Properties of Un-weighted Index Numbers:

• Equal Importance to All Items

Un-weighted index numbers treat all items in the dataset with equal importance, regardless of their actual usage, cost, or impact. This means a low-cost or rarely used item influences the index as much as a high-cost or frequently used item. While this simplifies calculations, it can distort the true picture of economic trends. This property limits the accuracy of un-weighted indices in reflecting real-life consumption or production patterns.

• Simplicity in Calculation

Un-weighted index numbers are easy to compute because they do not require additional data like weights or quantities. Only the prices or quantities from the base and current periods are needed. This simplicity makes them ideal for quick estimates or introductory statistical analysis. However, this ease comes at the cost of precision and relevance, especially when different items have significantly varied importance or impact in the real-world context.

• Distorted Representativeness

Because they assign equal weight to all items, un-weighted index numbers may give a distorted representation of overall price or quantity changes. For instance, a major change in a high-volume product could be overshadowed by minor changes in several low-impact items. This lack of representativeness means that un-weighted indices can mislead policymakers or businesses if used for serious economic or financial decision-making.

• Limited Real-World Application

Due to their disregard for item importance, un-weighted index numbers have limited use in actual business or economic analysis. They are mostly used for academic or theoretical purposes, such as teaching basic statistical concepts. In practical scenarios like inflation tracking or market analysis, weighted index numbers are preferred as they offer a more realistic and reliable measure of change based on actual consumption, sales, or production data.

Types of Un-weighted Index Numbers:

• Simple Aggregative Index Number

This method calculates the index by summing the current period prices and dividing them by the sum of base period prices, multiplied by 100. The formula is:

Simple Aggregative Index = (∑P1 / ∑P0) × 100

Where P1​ and P0​ are current and base period prices. All items are treated equally, regardless of their significance. While easy to compute, it can be misleading if high-priced items disproportionately affect the result. It is suitable for basic analysis but lacks real-world precision.

• Simple Average of Price Relatives Index

This method calculates the price relative for each item (current price divided by base price × 100) and then takes the arithmetic mean of all these relatives. Formula:

Simple Average of Price Relatives = [∑(P1 / P0×100)] / n​

Where $n$ is the number of items. This approach ensures each item has equal influence on the final index, regardless of actual importance. It’s more refined than the aggregative method and reduces the impact of extreme values, but still does not reflect real consumption patterns or weights.