The call center began calling the D2 households within the first 1 to 2 weeks of fieldwork, and the enumerators began bi-weekly visits to the D1 households within the same time frame. Given the relatively small sample size, the length of each phone call (with an average of approximately 5 minutes), and the required frequency of the calls per week, two phone operators ran the call center dividing the D2 households among themselves. The calls were meant to serve the same objectives of in-person visits, and at each call, the operators asked respondents to report to them the last recorded harvest in their diary. The call center carefully tracked which households were harvesting at a given time to ensure that they did not miss the opportunity to remind respondents to fill their data. Each respondent could additionally call his/her assigned enumerator and the associated supervisor, whenever needed. Furthermore, when diaries were collected at the end of each month, the enumerators sat down with the D2 respondents to review their diaries.

Furthermore, since only 42 percent of rural households in Malawi had been estimated at the time of the CVIP design to own a working mobile phone, each D2 household was given a mobile phone with a solar charger.<sup>20</sup> This package was valued at approximately US$29 (US$16 for phone, and US$13 for the solar charger). This was a critical decision to incentivize participation and ensured that all households were treated equally irrespective of their mobile phone ownership. The phones distributed to the D2 households were kept as simple as possible to make sure the respondents retained the asset for the duration of the survey while still maintaining adequate battery life and durability. Further, each D2 household was provided a total airtime incentive of approximately US$7, distributed in monthly installments. These decisions were in line with the recommendations of Dabalen et al. (2016) and were taken to ensure that the phones remained active and that the respondents stayed motivated.

Finally, each D1 and D2 household was provided with sacks and a hanging weighing scale to record the fresh cassava harvest in their diaries in kilograms. During the first interview, the diary respondents were trained in the use of the diaryP20F<sup>21</sup> and the weighing scale. Each scale was valued at approximately US$10 and was left with the household at the end of the fieldwork period. The sacks provided to the diary households were valued at approximately US$4. Overall, the total value of the incentive package was approximately US$20 for the D1 households, and US$53 for the D2 households, as shown in Table 1.

# **3.1.2. Recall Arms**

The third group of households (R1) were visited twice over the course of the 12-month fieldwork, with 6 months in between visits. At each visit, the R1 households were asked to report cassava

> 20 According to the authors’ calculations based on the Fourth Integrated Household Survey (IHS4) 2016/17, only 11 percent of households in Malawi have access to electricity.

> 21 Enumerators distributed paper production diaries leading up to the start of each calendar month. Following the collection of the paper diaries from the prior month, the supervisors for each district entered the data into the Survey Solutions CAPI platform. A second data entry and verification of the paper diaries took place in September 2016.

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