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<h2>SARs Newsletter</h2>

<h2>Number 19 Insert - March 2003</h2>

<h3>Adding Geography back to the SAR</h3>

<p>Many users need to know about the district-level distributions of population characteristics not captured by planned standard census outputs.  For this reason, they have requested district-level coding for the SAR.  Unfortunately, as noted in the latest SAR newsletter, sub-regional geographic coding had to be sacrificed in the trade-off between SAR content and respondent confidentiality.  
</p>

<p>To help compensate for this loss, it is planned to add pseudo-LAD indicators to the SAR.  These pseudo-LAD indicators will allow users to quickly and easily extract statistical best estimates of unknown district-level distributions from the SAR.  The resulting estimates will normally be at least as accurate as those derived using Iterative Proportional Fitting, a statistical technique commonly adopted in such circumstances.
</p>

<p>The proposed pseudo-LAD imputation strategy will identify the set of individuals in the SAR that 'best represent' each SAR district.  Specifically, when aggregated at district level, the identified set of individuals will

<ol>
	<li>accurately reproduce a set of a dozen or so published district-level Census tabulations.  These tables, acting as constraints on the imputation process, will involve the interactions between a dozen or so Census variables.</li>

	<li>provide best estimates for other unknown district-level distributions, provided that they involve interactions between table marginals used in (i).</li>
</ol>

Full details of the proposed methodology, including a statistical assessment of estimate accuracy, may be found at <a href="http://pcwww.liv.ac.uk/~william/microdata">http://pcwww.liv.ac.uk/~william/microdata</a>.
</p>

<p>The initially proposed list of variables from which reliable district-level estimates can be derived are as follows:

<table>
	 <tr>
		 <td>Demographic
		 </td>
		 <td>
			 Age<br />
			 Sex<br />
			 Marital Status<br />
			 Household composition (adults/children)<br />
		</td>
	</tr>

	<tr>
		<td>Cultural
		</td>
		<td>
			Ethnic Group<br />
			Religion<br />

		</td>
	</tr>
	<tr>
		<td>Economic
		</td>
		<td>
			Economic activity<br />
			NS-SEC (2001 version of 'social class')<br />
			Cars in household<br />

		</td>
	</tr>
	<tr>
		<td>Housing	
		</td>
		<td>
			Dwelling type<br />
			Tenure<br />
			Rooms in household<br />
		</td>
	</tr>
</table>
</p>

<p>Please send suggestions for possible alternative/additional constraining variables to Margaret Martin, CCSR, University of Manchester, M13 9PL, or email: margaret.martin&#64;&#109;&#97;&#110;&#46;&#97;&#99;&#46;&#117;&#107; 
</p>



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