Comparing Diary and Recall Methods in Tanzanian Poverty Measurement: Key Insights

The study compares diary and recall methods for collecting food consumption data in Tanzania, finding significant differences in reported expenditures but minimal impact on poverty measurement. It underscores the need for careful consideration of data collection methodologies in poverty assessments.

A recent research by Akuffo Amankwah, Darcey Jeanne Genou Johnson, Josephine Ofori Adofo, Maryam Gul, and Amparo Palacios-Lopez, is a significant contribution from the World Bank Group, specifically from its Development Data Group and the Living Standards Measurement Study team. The paper delves into how different methods of collecting food consumption data namely a 14-day diary and two variants of a 7-day recall impact the measurement of poverty in Tanzania. The study's importance is underscored by the ongoing global push to harmonize poverty measurement methodologies to ensure comparability across countries and regions.

A Nationwide Experiment in Tanzania

The researchers conducted a nationally representative randomized survey experiment in Tanzania, a country where poverty measurement is crucial due to its economic conditions and the high proportion of the population engaged in informal and seasonal jobs. The experiment aimed to compare the diary method, traditionally used in Tanzania’s Household Budget Survey (HBS), with the 7-day recall methods employed in the National Panel Survey (NPS). The diary method involves households recording their daily food consumption over two weeks, while the recall methods ask respondents to remember their food consumption over the previous week. This study is particularly timely as regional bodies, like the East African Community, are advocating for standardized methodologies across member countries to improve data comparability.

Discrepancies in Food Consumption Reporting

One of the key findings of the study is the significant difference in food consumption expenditures reported by the two methods. The diary method, despite capturing a broader range of food items, consistently reports lower total food consumption expenditures compared to both recall methods. This discrepancy is attributed to several factors, including the potential for recall methods to overestimate consumption due to respondent memory lapses or social desirability bias. On the other hand, the diary method, though more detailed, might underreport expenditures due to respondent fatigue over the two-week recording period. Despite these differences in reported expenditures, the study finds that the choice of data collection method has a limited impact on poverty rates when measured at various thresholds. The poverty rates remain statistically similar across the diary and recall methods, suggesting that while the method affects expenditure reporting, it does not drastically alter the overall poverty measurement.

Analyzing the Methodological Differences

The study's design involved both descriptive and regression analyses to assess the differences between the methods. The descriptive analysis showed that households using the diary method consumed a wider variety of food items, which is consistent with previous research indicating that open-ended data collection methods capture more diverse consumption patterns. However, the diary method’s lower expenditure figures could be explained by the potential decline in recording accuracy over time as respondents become fatigued. In contrast, the recall methods, particularly the variant with a longer list of food items, yielded higher reported expenditures. This outcome suggests that while recall methods might be more practical and less burdensome for respondents, they may also lead to inflated consumption figures due to the limitations of human memory and the structure of recall questionnaires.

Insights into Non-Food Expenditure Patterns

Furthermore, the study reveals that non-food consumption expenditures were relatively similar across all methods, with no significant differences observed. This finding implies that the variations in total consumption expenditures are primarily driven by differences in food consumption reporting. The analysis also indicated that household characteristics, such as the level of education and type of employment of the household head, play a role in influencing the accuracy of reported expenditures, particularly in the recall methods.

Implications for Policy and Poverty Measurement

The implications of this study are profound for policymakers and international organizations involved in poverty measurement and development policy. The results suggest that while recall methods might be more cost-effective and easier to implement on a large scale, they may not always provide the most accurate picture of consumption patterns. On the other hand, the diary method, although more demanding in terms of respondent engagement and data collection resources, could offer a more nuanced and potentially more accurate understanding of poverty, especially in capturing the diversity of food consumption. These findings underscore the importance of carefully considering the trade-offs between different data collection methodologies when designing household surveys for poverty measurement.

The study provides valuable insights into the complexities of measuring poverty through household surveys and the potential implications of choosing one data collection method over another. It highlights the need for a balanced approach that considers both the practicalities of survey implementation and the accuracy of the data collected, particularly in contexts where poverty measurement is critical for informing policy decisions and international comparisons. As global and regional bodies continue to push for harmonized poverty statistics, this research offers a crucial evidence base for making informed decisions about the best methodologies to adopt.