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Postharvest (PHL) loss reduces the amount of food that is available to households, which can affect household food security. Postharvest loss may occur at various stages: 1) during harvest from mechanical damage and spillage; 2) during postharvest handling, including damage in storage (rodents, pests, rotting) and during drying and winnowing; 3) during processing; 4) through distribution and marketing; and 5) during consumption (FAO, 2011; Kaminski and Christiaensen, 2014). With advances in technologies that are affordable, reducing postharvest loss is a growing initiative to increase returns on investment for farmers (Zorya et al., 2011). There has been a debate on how to measure PHL to ensure that there is comparison of loss across different crops and how loss may vary at different stages in the product life cycle. Some studies have used loss of food as expressed in calories (Lipinski et al., 2013) and other studies express loss in terms of percent of weight (FAO, 2011). This may be an analytical aspect to consider in analysis. Survey tools have in the past focused on postharvest loss at harvest and during storage for a particular season. At the household level in agricultural surveys, less emphasis is made on enumerating losses in processing food and during the marketing process, but there is an interest in loss of food while crops are in the field (Kaminski and Christiaensen, 2014). The latter has been enumerated looking at whether there was loss of crops as they were awaiting harvest but there is no emphasis on the quantity lost since it would be difficult for the farmers to estimate.
How to operationalize the metric
Method of data collection and data needed to compute the method:
Data to estimate this metric are collected using a survey. In standard survey tools, the focus is too discover if there was a loss, what were the causes, and how much was lost. Following are sampe questions (NBS, 2014):
- Was any portion of production lost postharvest?
- What was the reason for the loss (rotting, insects, pests, theft, other)?
- Out of 10 units, how many were lost?
- What was the value of the lost crop?
Unit of analysis:
The unit of analysis is the percentage of harvest that was lost. This can be obtained from the question 3.It is important to perform quality checks of the data, for example, to remove data errors as well as typographical errors (some enumerators may enter percentages instead of unit from 1 to 10).
Limitations regarding estimating and interpreting:
In the new versions of surveys, data are enumerated on preharvest losses in the field and not much is enumerated on losses due to processing and marketing. There may be an over estimation of postharvest losses, depending on definition, if the farmer assumes that there is need to include all the losses incurred from harvest to marketing and the researcher is only focused on premarketing losses (Kaminski and Christiaensen, 2014). This issue may be addressed during enumerator training. Additionally, farmers that incurred small losses may not be inclined to report them and this may underestimate the PHL for the population.