impacts of acute illness during the experimental survey than the 300 households in the original observational survey. These results are reassuring in terms of the comparability of the two samples and the possibility that repeated surveys may have altered health behavior; at least these broad indicators suggest that households were behaving very similarly when we first visited them and when we followed up eight years later.

# **Section II: Recall period and health measures**

Table 2 shows the differences in means for the main outcome variables between the weekly and monthly recall for the observational and experimental samples. It provides a benchmark from which progressively more detailed specifications deal with, in Tables 3 through 5, respectively: 1) time invariant individual fixedeffects and seasonal effects in a difference in differences specification, 2) variation in recall effects by total number of episodes, and 3) possible biases introduced by modeling alternative patterns of missing values that are more frequent in weekly than monthly data.<sup>9</sup> As is clear from the table, the response from the monthly-recall group is lower than that of the weekly-recall group for every outcome variable. Furthermore, with only the exception of time spent sick with an acute illness, the estimated differences between the experimental and observational results are virtually identical at similar levels of statistical significance. The tests between the weekly and monthly data are precisely estimated, and the differences between the methods are robust. For time spent suffering from an acute illness, both methods show that the results from monthly recall are significantly different from those from weekly recall, just at slightly different rates.<sup>10</sup> On every dimension, the declines due to monthly reporting are large and important behaviorally. The number of acute illnesses declines by 0.6 illnesses per person-month or just over 60 percent. This measure may be contaminated if episodes last longer than a week (and are thus double-counted in the weekly but not the monthly data). However, consistent with the total acute illness result, we find that the probability of reporting any acute illness also declines by close to 15 percentage points in the monthly-recall surveys. Given base probabilities in the weekly-recall surveys of 47 (45) percent in the observational (experimental) data, this suggests that close to a third of all acute episodes are ―forgotten‖ once the recall period is increased to a month. Similarly, the total number of doctor visits declines by 0.16 (observational) and 0.18 (experimental) visits per month or 37 percent of the base weekly probabilities. As is clear from decomposition of doctor

> 9 In the experimental sub-sample, all respondents received weekly surveys in the first month and were allocated to weekly and monthly-recall groups in the second month. Therefore, if morbidity was lower in the second month due to seasonal effects, this would upwardly bias the differences due to the recall period.

> 10 In combination with Appendix Table 1, the means also suggest that despite the many surveys that households participated in, there was no change in overall morbidity or the probability of seeking treatment (for evidence of behavior change from surveys, see Zwane and others, 2011). This could be because our survey covered a number of different topics and did not ask respondents about specific behavioral actions.

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