To understand why the categories of food and energy are more sensitive to price changes, consider environmental factors that can ravage a year’s crops, or fluctuations in the oil supply from the OPEC cartel. Each is an example of a supply shock that may affect the prices for that product. However, although the prices of those goods may frequently increase or decrease at rapid rates, the price disturbances may not be related to a trend change in the economy’s overall price level. Instead, changes in food and energy prices often are more likely related to temporary factors that may reverse themselves later.
To demonstrate just how volatile energy prices, for example, can be relative to other prices less food and energy, Chart 1 compares the fluctuations of these two measures over time.