Since the posted question is tagged as 'american-english', and since Fowler's Modern English Usage is a British English style guide, I am venturing to supplement Andrew Leach's succinct and useful answer with similar advice from an array of U.S. style guides.
From Words into Type, third edition (1974):
Suspended compounds. When successive compound adjectives have one component the same in all, this component is sometimes omitted in all except the last. The best method is to retain the hyphen in each one.
...that cut across all such school- and book-imposed subject lines.
From the U.S. Government Printing Office, A Manual of Style (1986):
6.23. Where two or more hyphenated compounds have a common basic element and this element is omitted in all but the last term, the hyphens are retained.
2- or 3-em quads, not 2 or 3-em quads
2- to 3- and 4- to 5-ton trucks
2- by 4-inch boards, but 2 to 6 inches wide
6.4-, 3.1-, and 2-percent pay raises
moss- and ivy-covered walls, not moss and ivy-covered walls
long- and short-term money rates, not long and short-term money rates
From The New York Times Manual of Style and Usage, revised and expanded edition (1999):
hyphen. ... Use the suspensive hyphen, rather than repeat the second part of a modifier, in cases like this: On successive days there were three-, five-, and nine-inch snowfalls.
From Mark Davidson, Right, Wrong, and Risky: A Dictionary of Today's American English Usage (2006):
hyphens in suspension When hyphens join words to form a compound word, as in "round-the-clock availability," the hyphens are like links in a chain. But those hyphens may be partially unattached ("suspended") in a set of compound words that share the same end-word. For example, instead of "one-quart, two-quart, and three-quart cans," you may save space by using suspended hyphens: "one-, two-, and three-quart cans."
From The Associated Press Stylebook (2007):
SUSPENSIVE HYPHENATION:
The form: He received a 10- to 20-year sentence in prison.
From Garner's Modern American Usage, third edition (2009):
C. Suspensive Hyphens. When two phrasal adjectives have common element at the end, and this ending portion (usually the last word) appears only with the second phrase, insert a suspensive hyphen after the unattached words to show their relationship with the common element. The hyphens become especially important when phrases are compounded in this way—e.g.:
"Detroit is ... positioning the new class of compacts as the centerpiece of an old-fashioned, '50s- and '60s-style all-out autumn advertising blitz."
"Disney money also permitted Bob Weinstein to launch Dimension Films, a division devoted to the revenue-producing horror- and teen-movie market."
"It was a four- or five-times-a-year indulgence, if that."
And from The Chicago Manual of Style, sixteenth edition (2010):
7.84 Omission of part of a hyphenated expression. When the second part of a hyphenated expression is omitted, the hyphen is retained, followed by a space.
fifteen- and twenty-year mortgages
Chicago- or Milwaukee-bound passengers
but
a five-by-eight-foot rug (a single entity)
Although these U.S. style guides disagree to some extent about the preferability of using a suspensive hyphen versus repeating the end word in a series of compound modifiers that have a shared final element, they are unanimous in approving of what the original post here refers to as "leav[ing] a hyphen dangling" (as opposed to omitting it altogether) after the unique element in a pair or series of such modifiers.
Perhaps the most straightforward expression of this style advice appears in a British English style manual, The Oxford Guide to Style (2002):
Use hyphens to indicate an omitted common element in a series:
three- and six-cylinder models
two-, three-, or fourfold
upper-, middle-, and lower-class accents
echo-, endo-, and mesomorphs
countrymen and -women
I should note, however, that some U.S. style guides firmly oppose replacing a repeated element in a series with a hyphen if that element is not the end term (as in Oxford's example of "countrymen and -women"). For example, the same entry (7.84) from The Chicago Manual of Style cited above concludes with this comment:
Omission of the second part of a solid compound follows the same pattern.
both over- and underfed cats
but
overfed and overworked mules (not overfed and -worked mules)
