standard to US measure?

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. In the future, such a category may be adopted listing the
extremes, but also adding a normal temperature range found
throughout most of a country's territory.

What information sources are used for the country flags?

Flag designs used in The World Factbook are those recognized by the
protocol office of the US Department of State.

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 using official exchange rates (OER). Other sources
probably use one of the two. See the Notes and Definitions 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 by separate staffs.
Chiefs of State includes fewer countries but more leaders, and is
updated more frequently than The World Factbook, which has a much
larger database, and includes all countries.

Some percentage distributions do not add to 100. Why not?

Because of rounding, percentage distributions do not always add
precisely to 100%. Rounding of numbers always results in a loss of
precision--i.e., error. This error becomes apparent when percentage
data are totaled, as the following two examples show:

Original Data Rounded to whole integer

Example 1 43.2 43
30.4 30
26.4 26
---- --
100.0