statistical offices will have to rely on phone surveys to collect information from households on the crisis’s impact while avoiding any face-to-face contact.

Ideally, a phone survey uses a nationally representative sample frame, where, if possible, the first round is an (existing) face-to-face survey. Once completed, researchers conduct follow-up phone interviews at regular monthly, quarterly, or other intervals. The survey output contains repeated welfare observations for each household, often before and after welfare shocks caused by violence, displacement, drought, or other things.

Baseline face-to-face interviews serve two primary purposes. First, to construct more traditional household welfare metrics—for instance, poverty—and then follow up with short questions more suited for a phone interview regarding changes in welfare. Second, for households without phones, one can be provided so that follow-up interviews can be truly nationally representative, as opposed to only representing the population with phone access (see for example, Dabalen et al., 2016).

When face-to-face interviews are not possible, as in the Syrian Arab Republic or during the COVID-19 epidemic, survey firms or statistical agencies could conduct phone surveys using a list of phone numbers representative of the population with access to a phone. Such a list can be acquired from phone numbers collected in the last nationally representative survey conducted in a country (see for example, Himelein et al., 2015). Alternatively, if such a list either does not exist or is outdated, partnering with mobile phone companies can generate a sample frame.

Lastly, when a list of the phone-using population is not available, surveyors can collect phone numbers via random digit dialing (RDD). Survey firms have algorithms to randomly dial phone numbers until a household answers, after which the household is offered the opportunity to complete a survey. The World Food Programme (WFP) used this approach effectively in Yemen, completing surveys of 2,400 households every month over the entire course of the conflict in that country (WFP, 2018).

# <u>Data requirements and pitfalls</u>

There are two primary drawbacks to the telephone survey approach. First, phone interviews can only accommodate relatively straightforward questions and have to be much shorter than face-to-face interviews. For these reasons, phone interviews cannot produce more traditional welfare metrics, such as poverty. Straightforward indicators of deprivation—such as lack of access to food, school, sanitation, and medical care—are more suitable for phone data collection.

A second drawback to the phone survey approach is difficulty in obtaining a representative sample of phone numbers. Particularly when face-to-face surveys are not possible, surveyors must settle for a survey that only represents the population with access to a phone and covered by a phone network. In the absence of readily available registries of phone numbers (e.g. from past face-to-face surreys), it may be difficult to obtain phone numbers of the phone-using population once a large shock has occurred. Thus, in many cases, surveyors rely on RDD-based surveys, which introduce selection bias for certain outcomes (see for example., Abraham et al., 2009).

In MENA, where phone penetration rates are high, phone surveys can play a very important role in measuring (subjective) well-being. The phone survey approach is particularly useful in conflict-affected countries—such as Iraq, the Syrian Arab Republic, Yemen, and Libya—where it is necessary to rely on remote data collection methods. Phone surveys can also be useful in other MENA countries where high19