signs 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 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 of digits to present, the Factbook staff
assesses the accuracy of the original data and the needs of US
Government officials. All of the economic data are processed by
computer--either at the source or by the Factbook staff. The economic
data presented in The Factbook, therefore, follow the roundi