interview.<sup>12</sup> Lau et al. (2019) report slightly different conclusions, with IVR at 43 percent of the cost of CATI and SMS at 24 percent of the cost of CATI. Each of these studies suggests that phone surveys are substantially less costly than in-person survey implementation, and that CATI is among the most expensive modes among the options for phone-based survey implementation. However, with a suggested length of 5 to 10 items and a maximum length of 15 items, IVR and SMS surveys cannot accommodate the more complex interviews that are made possible in a 20 to 30 minutes conversation in CATI (Glazerman et al., 2020). In sum, given literacy and non-response considerations discussed previously, and the complexity of most agricultural surveys that cannot be easily accommodated by IVR and SMS surveys, CATI remains the preferred mode of phone surveys for agricultural data collection.

The structure of survey costs differs greatly between phone and in-person surveys, and specifically between CATI and CAPI. The main budget lines for in-person surveys are transportation, especially in agricultural surveys where teams travel to sparsely populated rural areas, and per diems for long fieldwork periods. These lines are mostly eliminated in phone surveys, for which total costs are heavily driven by fixed costs including personnel and the acquisition of tablets or computers.<sup>13</sup> Costs for the establishment of call centers, where they do not already exist, such as rental fees for the space, need be considered. Variable costs for phone surveys, primarily in the form of airtime, are marginal.

For reference, in the LSMS-supported phone surveys, incentives made up between 6 and 17 percent of the per-interview cost. In addition to incentives, it may be necessary to provide mobile phones to respondents in the sample who do not already have one. This is not possible if using RDD, or using a register of existing numbers, but could be a possibility in phone surveys that are using an in-person survey as a baseline. This decision should be carefully considered, as discussed in Section 3.1. Kilic et al. (2021) provided respondents with a mobile phone worth $15.71 and a solar charger worth $12.86. This is roughly double the combined value of the cash and airtime incentives they provided ($7.14 each). Given the low variable costs of phone surveys, they generally become even more cost effective when utilized for panel surveys, repeated cross sections, or when combining the use of a call center with other survey operations, thereby lowering the fixed costs on a per interview basis.

# 6. Discussion and conclusions

This paper explored how the lessons learned from the COVID-19 pandemic, as well as pre-pandemic, phone survey experiences can be used to inform the integration of phone-based data collection into the survey and data systems in low- and middle-income countries, with a specific focus on the surveys of interest to agricultural statisticians and economists. Several overarching findings emerged. First, given the remote nature of phone interviewing, respondent burden and attrition deserve particular attention, requiring simplified survey question formats as well as abbreviated interviewing durations. Second, limited and uneven mobile phone coverage remains a critical issue for rural and agricultural populations, which has the potential to bias survey estimates, making better coverage a priority and post-survey adjustments a necessity. Finally, phone surveys allow tailoring data collection to the timing of the agricultural season in a cost-efficient manner, which can improve the quality of agricultural data and

> 12 For CATI Henderson and Rosenbaum (2020) caveat these values with the indication that a “portion of these estimates do not include fixed costs and underestimate total survey costs”. They also report large standard deviations for both IVR and CATI.

> 13 For example, in the Nigeria LSMS-ISA survey, direct transport costs represented approximately 23 percent of the overall survey budget while these costs are nonexistent in the Nigeria HFPS.

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