f the people are younger than
this age and half are older. It is a single index that summarizes the
age distribution of a population. Currently, the median age ranges from
a low of about 15 in Uganda and Gaza Strip to 40 or more in several
European countries and Japan. See the entry for "Age structure" for the
importance of a young versus an older age structure and, by
implication, a low versus a higher median age.

Merchant marine: Merchant marine may be defined as all ships engaged
in the carriage of goods; or all commercial vessels (as opposed to all
nonmilitary ships), which excludes tugs, fishing vessels, offshore oil
rigs, etc. This entry contains information in four fields - total,
ships by type, foreign-owned, and registered in other countries.

Total includes the number of ships (1,000 GRT or over), total DWT for
those ships, and total GRT for those ships. DWT or dead weight tonnage
is the total weight of cargo, plus bunkers, stores, etc., that a ship
can carry when immersed to the appropriate load line. GRT or gross
register tonnage is a figure obtained by measuring the entire sheltered
volume of a ship available for cargo and passengers and converting it
to tons on the basis of 100 cubic feet per ton; there is no stable
relationship between GRT and DWT.

Ships by type includes a listing of barge carriers, bulk cargo ships,
cargo ships, chemical tankers, combination bulk carriers, combination
ore/oil carriers, container ships, liquefied gas tankers, livestock
carriers, multifunctional large-load carriers, petroleum tankers,
passenger ships, passenger/cargo ships, railcar carriers, refrigerated
cargo ships, roll-on/roll-off cargo ships, short-sea passenger ships,
specialized tankers, and vehicle carriers.

Foreign-owned are ships that fly the flag of one country but belong to
owners in another.

Registered in other countries are ships that belong to owners in one
country but fly the flag of another.

Military: This category includes the entries dealing with a country's
military structure, manpower, and expenditures.

Military - note: This entry includes miscellaneous military
information of significance not included elsewhere.

Military branches: This entry lists the service branches subordinate
to defense ministries or the equivalent (typically ground, naval, air,
and marine forces).

Military expenditures: This entry gives spending on defense programs
for the most recent year available as a pe