GDP measures the monetary value of all the goods and services produced within a country in a given period (say, a quarter or a year). It counts both private and public spending. The latter includes expenditures on infrastructure, education, health care, and defense. It also includes incomes from abroad, such as interest and dividends on investments. In principle, GDP equals market-based prices but it can be adjusted for price differences using purchasing power parity (PPP). GDP per capita is the metric most commonly used for comparisons among nations.
Economies grow at different rates and go through cycles. High-income countries (typically those in North America, Western Europe, Japan, and China) have the highest levels of GDP; low-income countries (typically those in Africa, Latin America, and East Asia) have the lowest. GDP is also affected by the “broken window fallacy,” which argues that spending to repair damage to the economy is good because it means people will be able to buy more things than they otherwise would, even though they may not need them.
The CIA World Factbook publishes GDP statistics for sovereign states, as well as for some non-sovereign entities—American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands. GDP figures for these territories are adjusted for population change and published quarterly and annually. They also include industry statistics. These figures are rescaled using implicit weights that are updated periodically, based on the results of economic surveys and other information. This process is called rescaling and it helps to make comparable series of data from different countries over time, although the rescaled GDP growth rates are not necessarily identical to those in the earlier editions that used an older base year for their implicit weights.