and subsequently keep these lists updated. Collecting phone numbers from more than one adult household member increases the chances of successfully re-contacting the household for any future survey. Updating and maintenance of the list of phone numbers may be done through brief follow-up calls or surveys though one needs to be mindful of inducing increased attrition via too many contacts. When possible, working with local officials or community leaders to update and maintain lists may be beneficial. This approach proved successful in increasing coverage ex-post in a recent World Bank Africa Gender Innovation Lab survey of rural agricultural households in Western Uganda (Sharma et al., 2021). An important additional consideration is to ensure that respondents can give informed consent to their phone numbers remaining on file for follow-up interviews (Glazerman et al., 2020).

In a situation where no recent previous phone contact information is available, survey designers can create a new sampling frame of phone numbers through in-person visits, listing households, their phone numbers, and some basic demographic information in target enumeration areas much like listing is done in traditional in-person surveys. The newly created lists can then be used for follow-up phone surveys.

Coverage at the household level may be increased by collecting contact information from a reference person outside the household, such as a friend, relative, or neighbor, particularly in situations when none of the household members own a phone. In the HFPS that drew upon the LSMS-ISA surveys, some of which used this approach, the availability of reference person contact information helped not only to retain households that do not have phone numbers of their own but also facilitated contact with households that could not be reached on their own phone(s) but were reached through a reference person’s. The share of HFPS respondents who were ultimately reached through reference person contact information ranged from 7 percent in Burkina Faso to 20 percent in Malawi. In all cases, the share of respondents reached through reference contacts was higher for rural and agricultural households with a substantial 22 and 23 percent of agricultural households reached through reference contacts in Ethiopia and Malawi, respectively.

Another strategy to increase coverage and response rates is by providing free phones to respondents. This strategy was used by the World Bank for its Listening to Africa (L2A) series of evaluations as well as by other researchers for individual experiments or impact evaluations (Dabalen et al., 2016; Dillon, 2012; Gaddis et al., 2021; McCullough et al., 2020). Beyond the cost implications of this strategy, providing mobile phones may meaningfully affect respondent behavior which the survey is seeking to measure and therefore interfere with the survey objectives or experimental design. Survey designers and researchers should carefully consider the implications of providing phones to respondents. An approach to limit this effect is to hand out phones to certain reference contacts in each community which can then connect selected respondents with interviewers.

One method to improve the chances of successful contact and interview with a respondent is to arrange some automated pre-contact to the sample units, typically and perhaps easiest through SMS message. This pre-contact can help to inform respondents of the survey as well as when they can expect a followup call for the interview. With this information, respondents may be more willing to answer a call from an interviewer and more closely monitor their phone if the call is expected. Pre-contact SMS messages have been shown to reduce nonresponse and enhance cooperation among phone survey respondents (Dal Grande et al., 2016).

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