In general, the LSMS-ISA longitudinal samples coincide totally or partially (i.e., as a subsample) with an existing agricultural or household sample survey. For instance, the Ethiopia Socioeconomic Survey (ESS) interviewed a subset of agricultural households from the existing Agricultural Sample Survey (AgSS), complementing its exclusively rural sample with a sample of urban EAs. The Tanzania National Panel Survey (NPS) and the Uganda National Panel Survey (UNPS) are composed of a subset of EAs drawn from household budget surveys, namely and respectively the Tanzania Household Budget Survey (THBS) and the Uganda National Household Survey (UNHS). In Malawi, the Integrated Household Panel Survey (IHPS) tracked and reinterviewed a subsample of households from the Third Integrated Household Survey (IHS3). In Nigeria, the General Household Survey-Panel (GHS-Panel) is a subsample of the GHS core cross-sectional survey. Finally, in Niger, the longitudinal study followed the entire sample of the National Survey on Household Living Conditions and Agriculture (ECVM/A).

The LSMS-ISA surveys consist of two-stage probability samples which use the general population census for their sampling frame. In most samples of the LSMS-ISA, enumeration areas (EAs) are selected as primary sampling units with probability proportional to size. A sample of households is then randomly chosen from the complete listing of households in the selected EAs. Thus, the LSMS-ISA sample constitutes a random sample of EAs, households, and individuals.

The LSMS-ISA samples are meant to be nationally representative of households and of individuals. Ideally, longitudinal studies preserve representativeness over time, indicating that the sample should represent both the current population at each survey occasion and the dynamics over time of the initial population. To maintain both types of representativeness, longitudinal surveys follow up with people interviewed in previous survey rounds and add new individuals to ensure that new members of the population such as migrants and newborns are included (Glewwe and Jacoby 2000). To this end, panel surveys establish rules to define interview targets in follow-up rounds and create specific protocols to track households and individuals that move away from their original location. Moreover, they adopt refreshed samples (i.e., rotating panel or split panel) and protocols for the inclusion in the survey of individuals not previously involved in the study.

When discussing tracking in panel surveys, Witoelar (2011) introduced the concept of interview targets and tracking targets. Interview targets are those that need to be interviewed; tracking targets are those individuals or households that should be tracked if they have moved and, if found, should be interviewed. Similarly, the author distinguished between following-up rules and tracking rules in defining the criteria for individuals or households to be interviewed depending on whether they are found in the same location or are movers. To some extent, the LSMS-ISA panel surveys can be seen as a panel of both households and individuals. All households and individuals found and interviewed during the baseline are interview targets across the entire history of the panel sample.

The LSMS-ISA tracking approaches are more heterogeneous and mainly diverge in terms of: (i) targeted tracking units, (ii) characteristics of the tracking targets, and (iii) geographical scope of the tracking. Decisions across these three elements will impact representativeness and cost.

The LSMS-ISA are heterogenous in terms of the unit targeted for tracking and reinterviewing. Usually, these panel surveys have tracked dwellings, households, or individuals, with each option having its own distinct implications. In 2022, the Burkina Faso EHCVM revisited the dwellings previously visited in 2018/19. Nigeria and Ethiopia track and reinterview those households participating in the first wave of data collection but not individuals that split from the household. The Malawi IHPS, Tanzania NPS, and Uganda UNPS track individuals.

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