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st: RE: RE: carryforward

From   Nick Cox <>
To   "''" <>
Subject   st: RE: RE: carryforward
Date   Mon, 23 Jan 2012 17:58:47 +0000

If this method is one of imputing missing values that in practice will be varying by a constant that was the last observed value, then as Tony implies it clearly can be problematic. 

But the method of replacing missing values by previous non-missing values is one I often use with small datasets entered by hand. When the observations come in blocks, I only need to type in values for the first identifier in each block, and then -replace- appropriately. 

Sometimes datasets arrive like that too. Only the first value in a block of some blocked variable is explicit, so you have to fill in (or fill out) implied similar values.  


Lachenbruch, Peter

This method has been seriously questioned and gives very poor answers generally.  A true p-value may be reported anywhere from 0.01 to0.15 when it should be 0.05.  I strongly urge it not be used.

From: [] On Behalf Of David Kantor []

Once again, thanks to Kit Baum, a new version of -carryforward- is
available on SSC.
This upgrade adds the -if- and -in- qualifiers.
Actually, the upgrade was written a long time ago, but never got
uploaded until now. Sorry, if that was my fault.

-carryforward- carries values from one observation to the next,
filling in missing values.

-ssc install carryforward-

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