Box 1
Use of Current and Inflation-Adjusted Economic Data in this Report

An important issue in comparing Gross Domestic Product and economic data over time is determining how much of any increase or decrease is real and how much reflects price inflation or deflation. This report includes inflation-adjusted numbers (chained dollars) at the overall national level only. Inflation-adjusted data are unavailable for trade data by individual country, mode of transportation, and specific commodity detail; in these instances the report uses current dollar figures without controlling for inflation.

While adjusting for inflation is important to reflect the correct size of changes in the value of trade, foreign trade data at the country, mode of transportation, and commodity levels are not commonly presented in inflation-adjusted terms due to a number of factors such as foreign currency exchange rates, business cycles, balance of payments, stock market news, and central bank policies, which affect the prices of specific goods and services traded internationally. Due to the complexity of the factors that influence international trade, it is difficult to control for trading partners' inflation rates as well as currency exchange fluctuations.

SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, June 2005.