The studies assessing the relative accuracy of recall vis-à-vis diary- or crop cutting-based approaches to data collection on crop production and yields are few and far between.P4F<sup>5</sup> Deininger et al. (2012) compare recall- versus diary-based estimates of cassava production, captured as part of a national crop diary operation integrated into the Uganda National Household Survey (UNHS) 2005/06. The documented magnitude of discrepancies between the two methods are especially high for cassava. Specifically, the authors show that recall underestimates both the householdlevel incidence of cassava cultivation and the value of cassava production by 28 percent and 24 percent, respectively. And Deininger et al. (2012) acknowledge that these already large discrepancies may constitute a lower bound given the 6-month duration of the diary operation and the fact that cassava can be harvested over a longer period. In the context of Malawi, at the macrolevel, the extent of discrepancies among the international databases, the ministerial data sources, and the national household surveys in terms of reported cassava production and yields further underscore the need for methodological research for improving the statistics on root, tuber and tree crops in general, and cassava in particular.

Considering the importance of cassava for food security and the absence of best practices in accurate survey data collection on extended-harvest crop production and yields, we present the results of a household survey experiment that randomly assigned sampled households in top cassava-producing districts in Malawi to one of four approaches to cassava production measurement over a 12-month period. These methods were: (1) daily diary-keeping, with semiweekly in-person supervision visits (D1) – the traditional gold standard in survey data collection; (2) daily diary-keeping, with semi-weekly supervisory phone calls (D2); (3) 6-month recall-based data collection in 2 visits that were 6 months apart (R1); and (4) 12-month recall-based data collection in a single visit (R2) – the current approach in Malawi and arguably the most cost effective practice for household and farm surveys collecting information on cassava production in low- and middle-income countries. Beyond the socio-economic and agricultural data collected on the sampled households, we leverage (i) the GPS-based areas of the cassava plots cultivated by the households, and (ii) the crop cutting data tied to a 5x5m sub-plot that was placed at random within a randomly-selected cassava plot of each household (regardless of the survey treatment) and that was harvested and weighed at the time of each household’s preference during the 12-month fieldwork.

The contributions of this work are fourfold. First, the results from this study provide another point of empirical evidence regarding the relative accuracy and cost-effectiveness of recall-based methods vis-à-vis their diary-based counterparts for household-level annual cassava production estimation. The findings feed into the guidance we provide on survey design for data collection on

> 5 The body of work investigating the accuracy of recall vis-a-vis diary extends beyond agricultural data. See, for instance, Beegle et al. (2012); Backiny-Yetna et al. (2017); Brzozowski et al. (2017); Friedman et al. (2017); and Troubat and Grunberger (2017) for the work on consumption data. Though less relevant for extended-harvest crops, Desiere and Jolliffe (2018) and Gourlay et al. (2017) document, in Uganda and Ethiopia, respectively, large (upward) biases in recall-based data on seasonal crop production and yield in comparison to crop cutting.

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