compared to hosts living farther away. To distinguish between host communities that are differentially affected by the arrival of the Rohingya, the CBPS sampling strategy used a threshold of three hours’ walking time<sup>16</sup> from a campsite to define two survey strata: (i) host communities with potentially high exposure (HE) to the displaced Rohingya, and (ii) host communities with potentially low exposure (LE).

# _Sample distribution among strata_

The decision on how to distribute the sample size across the three strata faced the classical dilemma of whether to distribute across strata according to their population shares (which would deliver nearly optimal estimates for Cox’s Bazar as a whole), or to allocate the same sample size to each stratum (which would deliver estimates of nearly the same quality for each stratum). Since both considerations were important, a 50/50 equal/proportional allocation between host and Rohingya displaced was chosen, following Aguilera et al. (2020). In other words, half the sample size was allocated to Rohingya displaced and half to hosts. Host communities were further distributed using a 50/50 equal/proportional allocation between high- and lowexposure communities. This procedure yielded 398 survey clusters: 200 clusters of refugee camps and 198 clusters of host communities equally distributed between high- and low-exposure areas. A full household listing was implemented in these clusters, and 13 households were then selected at random from each cluster for the survey. Table 4 shows the sample size at the design stage, as well as the realized sample size.

**Table 4: Intended and actual sample size by strata**

|**Stratum**<br>**Code**|**Stratum**<br>**Name**|**Distance**<br>**to site**<br>**(km)**|**Number of**<br>**mauzas**|**HHs**<br>**(census)**|**Pop**<br>**(census)**|**Number of**<br>**intended**<br>**clusters**|**Number of**<br>**actual**<br>**clusters**|**Number of**<br>**intended**<br>**households**|**Number of**<br>**actual**<br>**households**|
|---|---|---|---|---|---|---|---|---|---|
|**0**|Sites|Zero||213,198|909,120|200|192|2600|2496|
|**1**|High<br>Exposure|0.1 to 15|33|83,482|463,528|99|99|1287|1287|
|**2**|Low<br>Exposure|15.1 to<br>+45|33|256,776|1,381,963|99|96|1248|1248|
|**Total**|||**66**|**553,456**|2,754,611|**398**|**387**|**5174**|**5031**|

Note: HH = household. Each cluster includes 13 households

# <u>Sampling Rohingya displaced households</u>

For camps, high-resolution satellite imagery, together with population and household count data generated by the humanitarian agencies (UNHCR and IOM), provided the base for selection of EAs and the refugee sample. The sampling frame used for Rohingya displaced in camps was publicly available population counts from the IOM’s Needs and Population Monitoring (NPM) Round 12 Site Assessment, which provided the most recently updated refugee population data at the time of survey design.<sup>17</sup> The data available identified 34

> 16 Walkable roads and streets were mapped using OpenStreetMap (OSM) road networks. Three hours’ walking time roughly equals 15 kilometers.

> 17 NPM Round 12 was completed in October 2018, and the sampling strategy for this survey was finalized in December 2018.

10