First, and for those in doubt: hunger is a human rights violations (see article 25 of the Universal Declaration). Second, before we discuss ways to measure this violation, we have to know what it is that we want to measure. It’s surprisingly difficult to define hunger.
Definition of hunger
The word “hunger” in this context does not refer to the subjective sensation that we have when lunch is late. We’re talking here about a chronic lack of food or a sudden and catastrophic lack of food (as in the case of a famine). We measure a lack of food by measuring dietary energy deficiency, which in turn is computed based on average daily calorie intake. The FAO estimates that the average minimum energy requirement per person is 1800 kcal per day. The global average per capita daily calorie intake is currently about 2800 kcal. This average obviously masks extreme differences between the obese and the chronically undernourished.
The FAO minimum energy requirement per person of 1800 kcal is also an average. The minimum calorie need depends on many things: age, climate, health, height, occupation etc.
Usually, the concept of “hunger” as it is defined here is different from “malnutrition“. Hunger is a lack of food defined as a lack of calorie intake. Malnutrition is a lack of quality food, of micronutrients such as vitamins and minerals, and of a divers diet. Hence, people may have access to sufficient quantities of food and still be malnourished.
Hunger and famine are also different concepts. Hunger is a chronic and creeping lack of food, while a famine results from the sudden collapse of food stocks. A famine implies widespread starvation during a limited period. It can’t go on forever because it must stop when everyone has died or when food supplies are restored. Chronic hunger on the other hand can go on forever because it doesn’t imply widespread starvation. Of course, people do die of chronic hunger, and on a global level hunger kills more people than famines do. But whereas in the case of famine people die of starvation, the victims of chronic hunger usually don’t starve to death. When we say that hunger kills someone every 3.6 seconds we usually mean that this person dies from an infectious disease brought on by hunger. Hunger increases people’s vulnerability to diseases which are otherwise nonfatal (e.g. diarrhea, pneumonia etc.). In fact, most hunger related deaths do not occur during famines. Chronic hunger is much more deadly – it’s just not as noticeable as a famine. When and where famines occur, they are more deadly and catastrophic. But they occur, thank God, only exceptionally. Hunger on the other hand is a permanent fixture of the lives of millions and ubiquitous in many countries.
Measurement of hunger
Given this definition, how do we go about and measure the extent of chronic hunger? (The measurement of famine is a separate problem, discussed here). There are different possible methods:
- So-called food intake surveys (FIS) estimate dietary intake and try to relate this to energy needs determined by physical activity. Calorie intake below a minimum level means hunger. The problem here is that minimum calorie intake thresholds are somewhat arbitrary and do not always take people’s different calorie requirements into account. Even for a single individual, this threshold can vary over time (depending on the climate, the individual’s age, occupation and health etc.). Moreover, when trying to measure calorie intake, you’re faced with the problem of hunger due to imperfect absorption: it’s not because someone in a sample buys and consumes x number of calories that he or she actually absorbs those calories. The widespread incidence of diarrhea and other health problems often mean that only a fraction of calories eaten are absorbed by the body.
- In order to bypass this, some propose a measurement method based on revealed preferences. The greater the share of calories people receive from the cheapest foods available to them, the hungrier they are; and, conversely, the more they buy expensive sources of calories, the less hungry they are. Their choice of foods reveals whether they have enough calories. This method therefore eliminates the threshold and absorption problems.
Our approach derives from the fact that when a person is below their nutrition threshold, there is a large utility penalty due to the physical discomfort associated with the body’s physiological and biochemical reaction to insufficient nutrition. At this stage, the marginal utility of calories is extremely high, so a utility-maximizing consumer will largely choose foods that are the cheapest available source of calories, typically a staple like cassava, rice or wheat. However, once they have passed subsistence, the marginal utility of calories declines significantly and they will begin to substitute towards foods that are more expensive sources of calories but that have higher levels of non-nutritional attributes such as taste. Thus, though any individual’s actual subsistence threshold is unobservable, their choice to switch away from the cheapest source of calories reveals that their marginal utility of calories is low and that they have surpassed subsistence. Accordingly, the percent of calories consumed from the staple food source, or the staple calorie share (SCS), can be used as an indicator for nutritional sufficiency. (source, source)
- Still another method consists of measuring hunger’s physical effects on growth and thinness. Instead of measuring calorie intake, hunger or revealed preferences, you measure people’s length, their stunted growth and their body mass index. However, this is very approximative since length and weight may be determined by lots of factors, many of them unrelated to hunger.
- And finally there are subjective approaches. The WFP does surveys asking people how often they ate in the last week and what they ate, how often they skip meals, how far they are away from markets, if their hunger is temporary or chronic etc. Gallup does something similar.