applied in the case of Tanzania NPS 2012/13 (Figure 11); that is, respondents are slightly less likely to report having used fertilizer as the recall length increases.

# Recall error and other characteristics

While our focus is on the effect of the recall length on data quality, we always control for respondent characteristics, including via interactions with the length of the recall. Most of the respondent characteristics (age, education, gender, whether respondents are also plot managers) have no significant impact on the direction or magnitude of the effect of the recall length.<sup>11</sup> However, some are significantly correlated with our outcomes of interest. Female respondents tend to understate harvest and input quantities relative to male respondents. The same is true of respondents who are also plot managers (results not shown).<sup>12</sup> In contrast, respondent education is neither strongly correlated with levels of reported outcomes nor does it impact the recall length effect.

Unlike respondent characteristics, plot size consistently matters for the effect of recall length. In line with expectations, the recall effect on maize harvest quantity, labor and fertilizer inputs is attenuated, and sometimes even reversed, on larger plots in Tanzania NPS 2012/13 (Figure 14). Similarly, there is a significant interaction effect of recall length and plot size for harvest and fertilizer input in Malawi IHS4 and IHPS (Figure 15).

# Recall error and productivity measurement

This section explores the implications of the recall effect for agricultural productivity measurement, in which context the input and output variables discussed in this analysis are frequently studied. Interest is in three of the most common measures of agricultural productivity, yield (output per unit of land), output per day of work, and output per worker (

## Table 6 ).

The results discussed so far suggest that the impact of the recall length on the three productivity measures will vary. For yield (output per unit of land), the expected association is positive, since there is a positive effect of recall length on output (maize harvest), the numerator, while the plot area, measured with GPS, is not subject to recall error. For output per day of work, the results suggest an ambiguous effect. Both output, the numerator, and labor-days, the denominator, are positively associated with the recall length. The direction of the composite effect depends on which of the two dominates, and it is possible that there is no effect at all. Finally, for output per worker, the results suggest a positive recall effect. The recall effect on output, the numerator, is positive, and there is no effect on workers per plot, the denominator (

## Table 6 ).

> 11 Plots listed in the Malawi IHS4 cross section are the one case in which there is a significant interaction effect between respondent characteristics and recall length. Female respondents list fewer plots than male respondents (-0.52*** plots), but the effect of recall length is smaller among female respondents (-0.05** plots/month as opposed to -0.076*** plots/month).

> 12 Plot managers are presumably best informed about harvest quantities and inputs used, suggesting that self-reporting from female respondents may be more reliable than that from male respondents.

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