<p>The best way is taking the index "ingredients" and rebuild it... assuming you manage the index data on a DB or on an excel file, that should not be too difficult</p>

<p>Otherwise, assuming you're index ingredients are averaged equally, then in a sense, the index is calculated as:</p>

<pre><code>Index = (1 + Product1ChangeIn%)^(1/9) * (1 + Product2ChangeIn%)^(1/9) ...
</code></pre>

<p>So based on it, without coal, you're index should be:</p>

<pre><code>Index / (1 + CoalChangeIn%)^(1/9)
</code></pre>

CC BY-SA 4.0
2019-07-07T11:28:07.680Z
2019-07-07T11:28:07.680Z
Guy Louzon
<p>I have a producer price index which is the composite of 9 various commodity prices including that of coal. I want to remove the effects of coal price changes from the original index. I have data on coal prices. Does anyone know of a method that I could use to filter out the effects of coal price changes from the original index? </p>

CC BY-SA 4.0
2019-07-05T18:57:25.010Z
$P_{agg}-P_{coal}Q_{coal}$?
Herr K.
CC BY-SA 4.0
2019-07-05T21:41:20.977Z
Do you happen to know how the index is calculated (Paasche, Laspeyres, etc.), and the components (price changes, weights) for the individual components? Whether a particular method will work for your purposes depends on what information you have available to you.
dismalscience
CC BY-SA 4.0
2019-07-06T20:14:29.053Z
@dismalscience I don't know the method, but what if the index is an unweighted average of the commodity prices?
london
<macroeconomics><inflation><statistics><price-index>
Manipulating index numbers
london
# Manipulating index numbers

(Asked by: username_0 on 2019-07-05)

I have a producer price index which is the composite of 9 various commodity prices including that of coal. I want to remove the effects of coal price changes from the original index. I have data on coal prices. Does anyone know of a method that I could use to filter out the effects of coal price changes from the original index?

**Tags:** macroeconomics, inflation, statistics, price-index
> **Comments:**
> **username_1**: $P_{agg}-P_{coal}Q_{coal}$?  
> **username_2**: Do you happen to know how the index is calculated (Paasche, Laspeyres, etc.), and the components (price changes, weights) for the individual components? Whether a particular method will work for your purposes depends on what information you have available to you.  
> **username_0**: @dismalscience I don't know the method, but what if the index is an unweighted average of the commodity prices?  

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## 1 answers

### Answer by username_3 on 2019-07-07. Score: 1

The best way is taking the index "ingredients" and rebuild it... assuming you manage the index data on a DB or on an excel file, that should not be too difficult
Otherwise, assuming you're index ingredients are averaged equally, then in a sense, the index is calculated as:
Index = (1 + Product1ChangeIn%)^(1/9) * (1 + Product2ChangeIn%)^(1/9) ...

So based on it, without coal, you're index should be:
Index / (1 + CoalChangeIn%)^(1/9)


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