This is from the 2004 AP Stylebook:
Metric System
In general, metric terms should be included in a story when they are relevant.
There are no hard-and-fast rules on when they are relevant, but the following
two guidelines have been developed to cover questions likely to arise as metric
measurements gain increased acceptance in the United States:
-Use metric terms when they are the primary form in which the source of a
story has provided statistics. Follow the metric units with equivalents in the
terms more widely known in the United States. Normally, the equivalent should
be in parentheses after the metric figure. A general statement such as: A
kilometer equals about five-eighths of a mile, would be acceptable, however, to
avoid repeated use of parenthetical equivalents in a story that uses kilometers
many times.
-Provide metric equivalents for traditional forms if a metric unit has
become widely known. As speedometers with kilometer markings become more
prevalent, for example, a story about speed limits might list miles per hour
and provide kilometers per hour in parentheses.
My impression from reading stuff from AP and other sources with similar
guidelines is that there are in fact "not hard-and-fast rules on when [metric
units] are relevant". I think I've shared with this group that I've seen
several recent pieces in the NY Times, which has similar guidelines, that cited
metric units throughout without parenthetical conversion. Others convert to US
units and don't mention the original metric units.
And maybe we can take some solace in the fact that this 2004 publication states
these guidelines are useful "as metric measurements gain increased acceptance
in the United States". I hope that's not a hold-over from the 1970 edition.
From: Norman & Nancy Werling
Sent: Friday, January 23, 2009 6:50 AM
To: U.S. Metric Association
Subject: [USMA:42415] An Associated Press article in today's Atlanta
Journal-Constitution
USMA list members,
Spanish energy company Acciona Energia will build a wind farm in Mexico which
will be the largest in Latin America.
The article was written by Mark Stevenson of Associated Press. It states that
the wind farm will be 6180 acres. When converted back to hectares that would
have been 2500 hectares. Don't you agree that Mark Stevenson was required to
convert those 2500 hectares to 6180 acres by the Associated Press, even had he
wanted to report using the metric measure?
Norm Werling
