London--Shares in VNU Communications Inc. fell to a two-year low of $31.02 Wednesday after the Anglo-Dutch publishing giant warned of slower earnings growth than expected and said it had a "significant decline in advertising" in the first half of the year. VNU officials said they expected at least 5% growth in cash earnings per share for the full year, compared with a previous forecast of low-double-digit growth. The warnings follow similar downward revisions earlier this year from VNU rivals United Business Media Inc. and Primedia Inc. The company warned that a deteriorating economy had prompted a sharp slowdown in ad revenues for its business information group, causing a 1% decline in revenues. VNU also said it had a dramatic decline in revenues at the Adweek Group of publications and had implemented cost-cutting measures to offset the downturn.