Index numbers
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This document discusses problems in constructing and using index numbers. It addresses several key issues: [1] the purpose of the index must be clearly defined; [2] the base period should be normal and not too distant in the past, and a decision must be made whether to use a fixed or chain base; [3] appropriate weights must be assigned to items to reflect their relative importance. Issues in using indexes include generalizing from a specific index, lack of transparency, effects of time spans, and inability to account for quality changes.
Index numbers
- 1. Introduction to Statistics PROBLEMS IN THE CONSTRUCTION AND USING OF INDEX NUMBERS
- 2. • 1. THE PURPOSE OF THE INDEX: -- THE INDEX MUST BE VERY CLEARLY, DECIDED – WHAT THE INDEX IS TO MEASURES AND WHY? -- EVERY INDEX IS OF LIMITED AND PARTICULAR USE.
- 3. 2. SELECTION OF A BASE PERIOD. Whenever index numbers are constructed a reference is made to some base period. The base period of an index number (also called the reference period) is the period against which comparisons are made.: (i) The base period should be normal one. The period that is selected as base should be normal, i.e., it should be free from abnormalities like wars, earthquakes, famines, booms, depressions, etc. However, at times it is really difficult to select year which is normal in all respects – a year which is normal in one respect may be abnormal in another .
- 4. (II) THE BASE PERIOD SHOULD NOT BE TOO DISTANT IN THE PAST. It Is Desirable To Have An Index Based On A Fairly Recent Period, Since Comparison With A Familiar Set Of Circumstances Is More Helpful Than Comparison With Vaguely Remembered Conditions. (III) FIXED BASE OR CHAIN BASE. While Selecting The Base A Decision Has To Be Made As To Whether The Base Shall Remain Fixed Or Not, I.E., Whether We Have A Fixed Base Or Chain Base Index.
- 5. 3. SELECTION OF APPROPRIATE WEIGHTS. -- The term ‘weight’ refers to the relative importance -- This is done by allocating weights. Thus, in the former case, no specific weights are assigned whereas in the latter case specific weights are assigned to various items. -- Giving equal importance to all the items and hence weights are unity. It is, therefore, necessary to adopt some importance to all the items and hence weights are unity. It is, therefore, necessary to adopt some suitable method of weighting so that arbitrary and haphazard weights may not affect the results.
- 6. ISSUES IN USING INDEX NUMBERS Generalizing from a specific Index: -- CPI ( How prices of particular combination of goods for particular Income people Lack Of General Knowledge: -- Detailed statements about concerning measurements. Effect of Time Span on an Index: -- Factors related to Index tend to change with Time Quality Changes: -- do not represent quality