of high costs. Pictorial diaries and other methods have been proposed to partly overcome problems of illiteracy (Wiseman _et al._ 2005). Also, respondent‟s fatigue raises concerns about administering extensive (consumption) diaries, particularly in urban areas and for relatively long reference periods, potentially resulting in selective survey compliance. In developing countries contexts, consumption diaries are being increasingly used and their accuracy _vis à vis_ recall methods tested (Ahmed _et al._ 2006, Beegle _et al._ 2010, Gibson 2002). However, as noted by Wiseman et al (2005) “much of the literature on diaries focuses on _empirical_ results as opposed to _methodological_ insights”. Moreover, despite their potential advantages, particularly for intercropping, crops (e.g. tubers and vegetables) where the harvest stretches over longer spells, and for plots cultivated by different individuals within the household, diaries have rarely been used in agricultural production. Whether they can complement or even provide an alternative to recall or crop cutting methods is remains an empirical question.

# **2.2. The diary experiment and modalities of its implementation in Uganda**

A high incidence of intercropping and prevalence of continuously harvested crops such as banana ( _matooke_ ), cassava, and sweet potato imply that accurately measuring crop output in Uganda has long been a challenge. Production statistics published by international organizations such as FAO and figures from national household surveys differ widely from each other. Such errors may be exacerbated by issues of survey design and implementation including interviews that occur long after the reference period, respondent fatigue, or poor enumerator training. To explore ways to improve agricultural production statistics and analyze potential sources and magnitudes of errors in standard household surveys, the Uganda Bureau of Statistics (UBOS) complemented the 2005/06 Uganda National Household Survey (UNHS) with a harvest diary. The UNHS is a standard multi-purpose household survey with a sample of some 7,500 households from 750 enumeration areas (EAs) which, in rural areas are mostly equivalent to villages. Information on agricultural production was collected in two visits, each covering one of the country‟s two main cropping seasons. The first and second visit collected data on agricultural production for July to December 2004 and January to July 2005, respectively.

We expect that having a diary would significantly reduce three sources of bias that might possibly have led to under-reporting of crop output. First, as it records output immediately upon harvest, _recall bias_ , whereby in interviews that occur long after the crop has been harvested respondents may under-report the actual amount of output obtained, should be minimized. Second, diaries are expected to reduce _respondent bias_ that might arise from the fact that recall surveys are implemented by a dedicated team that has limited time available for finalizing the interview and often interviews only one member of the household. Diaries, by contrast, can be regularly reviewed together with the local monitor and the danger that a household member other than the one responsible for production provides is asked to provide 5