Ah, the advent of Spring in the northern hemisphere! Green shoots, apple blossom, cavorting lambs and ... advertising seers sprouting prognostications of future adspend trends.

Welcome to the ancient annual rite of the crystal balls, inaugurated this year, as ever, by media planning and buying network ZenithOptimedia.

In general, it looks to be roses, roses all the way. Zenith is bullish about 2005, revising upward its earlier global growth forecast from 5% to 5.4%. In 2006, overall adspend will grow by 6.5% only to slip back to 6.1% in 2007.

But future prospects are not so rosy for the TV business where Zenith predicts growth will peak in 2006 with a 37.9% share of the total advertising market - followed in 2007 with a decline to 37.8%. It attributes this to the diversion of advertising funds to online media.

Comments Zenith: "We record only one previous instance in which television's share of world adspend declined, and that was when the dotcom bubble burst in 2001."

And it is the internet that continues to make the pace in terms of adspend growth. Leading all other media sectors, online advertising grew 21% in 2004, a trend Zenith expects to continue in double-digit terms for at least another three years.

Traditional media too are enjoying the good times (while they last), albeit at a less spectacular pace. In 2004 worldwide adspend grew by 7%, spurred by the Athens Olympics and the US presidential election.

But advertising, like the seasons, has its cycles. Adland's spring will eventually cede to fall warns Zenith. Current year growth, predicted at 5.1%, will fruit in 2006 with a 6.2% uplift, declining in 2007 to 5.7%.

And that's the advertising weather forecast. There'll be several more before April melds into May.

Data sourced from BrandRepublic (UK); additional content by WARC staff