etric 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?

GDP dollar estimates in The World Factbook are derived from purchasing
power parity (PPP) calculations. See the Notes and Definitions section
on 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 99

Example 2 42.8 43
31.6 32
25.6 26
---- --
100.0 101

When this occurs, we do not force the numbers to add exactly to 100,
because doing so would introduce additional error into the
distribution.

What rounding convention does The World Factbook use?

In deciding on the number o