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 rounding convention used by virtually all numerical software applications, namely, any digit followed by a "5" is rounded up to the next higher digit, no matter whether the original digit is even or odd. Thus, for example, when rounded to the nearest integer, 2.5 becomes 3, rather than 2, as occurred in some pre-computer rounding systems.