There are many ways to describe trends in an important subject such as world hunger. Figur...

There are many ways to describe trends in an important subject such as world hunger. Figure 9.2 shows two views of this problem: total number and proportion of the population. Another approach is to compare values to a standard value. For example, you could compare all years to 1969, to see how hunger has changed since 1969, when reliable statistics were first gathered by the UN Food and Agriculture Organization (FAO).

These adjusted numbers are index values, or values adjusted to be on the same scale or magnitude. In figure 1, index values were created by dividing all values for a region by the 1969 value. The 1969 value (divided by itself) becomes 1. All other values are either larger or smaller than 1.

Why would you want to adjust values to the same magnitude, rather than show original numbers? One reason might be that values vary a great deal among regions, and it’s hard to compare trends on the same graph. Another reason is that you might be more interested in the amount of change than in the absolute numbers. That is, you know there are a lot of undernourished people in sub-Saharan Africa, but you might want to know if the situation is getting worse or better compared to some baseline condition.

FIGURE 1 Number of people chronically hungry. Index values show change relative to a baseline value (the 1969?71 average).

Source: UN FAO, 2011.

FIGURE 2 Food prices in India, relative to 1980. Index values show prices paid to Indian farmers for products (adjusted for inflation).

Figure 2 on this page shows prices paid to farmers in India for four main foods. In general, have food prices increased or declined? What other factors might influence affordability of food?