US Federal agencies are required by the Metric Conversion Act of 1975 (Public Law 94-168) and by Executive Order 12770 of July 1991 to use the International System of Units, commonly referred to as the metric system or SI. In addition, the metric system is used by over 95 percent of the world's population.
Why don't you include information on minimum and maximum temperature extremes?
The Factbook staff judges that this information would only be useful for some (generally smaller) countries. Larger countries can have large temperature extremes that do not represent the landmass as a whole.
What information sources are used for the country flags?
Flag designs used in The World Factbook are based on various national and vexillological sources.
Why do your GDP (Gross Domestic Product) statistics differ from other sources?
We have two sets of GDP dollar estimates in The World Factbook , one derived from purchasing power parity (PPP) calculations and the other derived from official exchange rates (OER). Other sources probably use one of the two. See the Definitions and Notes section on GDP and GDP methodology for more information.
On the CIA Web site, Chiefs of State is updated weekly, but the last update for the Factbook was an earlier date. Why the discrepancy?
Although Chiefs of State and The World Factbook both appear on the CIA Web site, they are produced and updated on different weekly schedules. Chiefs of State includes fewer countries but more leaders, whereas The World Factbook has a much larger database and includes all countries.
Some percentage distributions do not add to 100. Why not?