Even if the additional requirements in staff weeks, number of moves, and days of lodging are added, the cost savings from the WMS with a subsample of consumption data seem significant. For example, if the subsample size is set at 640, the combination needs only 7 percent of staff weeks and days of lodging required for HIES data collection, although the number of moves needed for the combination is projected to be slightly higher, 110 percent of the HIES (table 12). The latter is due to separate data collections for consumption data and nonconsumption data. If the size of the subsample is set at 320, the WMS with a subsample of consumption data needs even fewer staff weeks, moves, and days of lodging.

# **Diary-Based Versus Recall-Based Consumption Data Collection**

As discussed above, there is potentially a large cost-saving effect by switching the current diary-based data collection to a recall-based collection. Currently, two enumerators need to visit each household seven times during their two-week stay in a PSU. This implies that if a two-week, recall-based collection is selected, in theory, an enumerator would need only two days to cover 20 households in a PSU. Since the number of households for a subsample of the WMS is reduced to 10 households, theoretically, one enumerator could collect consumption data from all 10 households in one day. In the cost projection above, we made a more conservative assumption—that one staff week would be needed to collect consumption data from all households in each PSU. As a result, if the subsample size is set at 640, then the WMS with a subsample of consumption data needs a total of 370 staff weeks, 676 moves among PSUs, and 2,590 days of lodging, which correspond to 6 percent, 110 percent, and 6 percent, respectively, of the HIES.

As mentioned earlier, how consumption data are collected affects how households respond. In general, we do not know whether a switch from a diary-based collection to a recall-based collection increases reporting of consumption expenditures (Beegle et al. 2011). Such a switch often reduces consumption aggregates simply because households remember their expenses better when entering them regularly in a diary.

**Figure 3: Comparison of Distributions of Food Expenditures and Nonfood Expenditures between Diary-  and Recall-Based Data Collections**

<!-- Start of picture text --> Food<br>Recall<br>Outliers =1 if logY > 2.5 * sd(logY))+mean(logY) in each division.<br>Food<br>Diary<br>0 2000 4000 6000<br>Outliers =1 if logY > 2.5 * sd(logY))+mean(logY) in each division.<br>Taka, p.c.<br>Density Kernel density<br>Graphs by diary<br>.001<br>5.0e-04<br>0<br>.001<br>5.0e-04<br>0<br><!-- End of picture text --> <!-- Start of picture text --> Nonfood<br>Recall<br><!-- End of picture text --> <!-- Start of picture text --> .001<br>5.0e-04<br><!-- End of picture text --> <!-- Start of picture text --> Outliers =1 if logY > 2.5 * sd(logY))+mean(logY) in each division.<br>Nonfood<br><!-- End of picture text --> <!-- Start of picture text --> Nonfood<br>.001 Diary<br>5.0e-04<br>0<br><!-- End of picture text --> <!-- Start of picture text --> 15000<br><!-- End of picture text --> <!-- Start of picture text --> 10000<br><!-- End of picture text --> <!-- Start of picture text --> Outliers =1 if logY > 2.5 * sd(logY))+mean(logY) in each division.<br>Taka, p.c.<br>Density<br><!-- End of picture text --> <!-- Start of picture text --> Kernel density<br><!-- End of picture text --> <!-- Start of picture text --> Graphs by diary<br><!-- End of picture text --> _Sources_ : Authors’ estimations using pilot data.

To examine the effects of switching the method of collecting consumption data, the BBS and the World Bank conducted a pilot survey. To investigate the comparability of consumption aggregates when diarybased consumption data collection is replaced by recall-based collection, the two collection methods were randomly assigned to half of the households in each PSU. In four strata: Dhaka urban, Dhaka rural, Khulna rural and Rajshahi rural, 720 households from 60 PSUs (12 households from each PSU) in the 23