sample size for all primary sampling units (PSUs). In all surveys, an interviewer is assigned to each PSU and required to collect data from 104 sampled households per year. As pointed out in the introduction, there are 85 interviewers throughout Azerbaijan, leading to a total 8840 observations if all selected households were interviewed and their data retained. The fact that we have interviewer identification numbers in the data allows us to count the number of missing households (non responding households or households deemed to have unusable data) at the interviewer (i.e., PSU) level: _Nmisp = 104 - Nobsp_ Where Nmis _p_ denotes the number of missing households at PSU _p_ , and Nobs _p_ denotes the number of usable observations (households) available at PSU _p_ . If the part of the population that is left out is different than the part that is observed, there will be differences between the survey results and what is actually true in the population. Table 8 below shows the distribution of missing households at the regional level. The percentage of missing households is higher in urban areas than rural. There were more than twice as many missing households in 2002 than either 2003 or 2004, suggesting some improvement in response rate over time.

**Table** **<u>8.</u>** Distribution of missing households in Azerbaijan HIES data

|||**2002**<br>|||**2003**<br>|||**2004**<br>||
|---|---|---|---|---|---|---|---|---|---|
||Total<br>Sample|Missing|%<br>Missing|Total<br>Sample|Missing|%<br>Missing|Total<br>Sample|Missing|%<br>Missing|
|Azerbaijan|8840|683|7.7|8840|316|3.6|8736|311|3.6|
|Baku|2392|200|8.4|2392|159|6.6|2392|133|5.6|
|Non-Baku urban|2808|250|8.9|2704|84|3.1|2288|91|4.0|
|Rural|3640|233|6.4|3744|73|1.9|4160|87|2.1|
|Nakhchivan|520|49|9.4|520|23|4.4|520|10|1.9|
|Absheron-Guba|1040|152|14.6|1040|52|5.0|1040|53|5.1|
|Mughan_Salyan|728|52|7.1|728|10|1.4|728|12|1.6|
|Ganja-Gazakh|1144|63|5.5|1144|24|2.1|1144|32|2.8|
|Sheki-Zagatala|624|37|5.9|624|6|1.0|624|20|3.2|
|Lankaran_Astara|832|36|4.3|832|17|2.0|832|12|1.4|
|Shirvan|624|20|3.2|624|8|1.3|624|16|2.6|
|Qarabagh-Mil|1144|74|6.5|1144|17|1.5|1144|23|2.0|

Source: Azerbaijan HIES data.

Non-response or missing observations at the household level occur when a household or person selected for the survey does not participate in the survey or does participate but does not provide complete information. There can be many reasons for missing observations or non-response in survey data. A listed housing unit chosen for the sample may be found unoccupied when an interviewer visits the housing unit. Even if it is occupied, several adverse events may prevent data collection. Although a housing unit is occupied, its residents may be away from home during the entire survey period. Health conditions, whether permanent, such as hearing impairment or blindness, or temporary, such as an episode of a severe acute illness, may preclude an individual from responding as well. More importantly, a non-response also may occur when a person at home during the survey refuses to participate as an individual or as a representative of the entire unit.

From communications with Azeri officials with the knowledge of the HIES data, the predominant reason for non-response was refusal of the rich households to participate in the 10