I should have referred to something like [link|http://www.mit.edu/afs/athena/course/11/11.481j/www/Suggestions.html|this ] first:
14. Hyphenation of adjectives. The general rule for using hyphens with adjectives is: two or more adjectives should be hyphenated if when they are used alone the true sense of the modification is not clear.
Write--
The base-year data were obtained from an independent survey in Kenya.
Do not write--
The base year data were obtained from an independent survey in Kenya.
(It is not base data, nor year data, but base-year data that are being described.)
If there's a chance of it being misinterpreted, hyphens should be used. I'd have to check Gryg's text again to see if I'd suggest fewer hyphens.
Thanks.
Cheers,
Scott.