(Adds GroupM forecasts)
LONDON, Dec 8 (Reuters) - Two leading forecasters of globaladvertising trends trimmed their predictions for growth in adspending this year, due to a sharp slowdown in Russia andeconomic weakness in the euro zone.
Zenith Optimedia, owned by advertising agency Publicis, had downgraded its forecasts in September and cutthem again on Monday. They now expect global advertisingexpenditure to rise 5.1 percent in 2014 and 4.9 percent the yearafter.
The forecasts compare with September's downgradedexpectations of 5.3 percent increases in both years.
GroupM, owned by WPP, also trimmed its forecasts for2014 growth to 3.9 percent, down from 4.5 percent, due totougher than expected conditions in China, Brazil, Israel,Nigeria and Russia.
It expects growth in 2015 of 4.9 percent, slightly lowerthan its forecast for 5 percent made in August.
Zenith said advertisers in the major European markets ofFrance, Italy and Germany were holding back on spending, while the fall in the oil price had exacerbated the impact of theconflict in Ukraine.
Ad spend in the Russian market was forecast to grow just 1.8percent this year, following many years of double-digitincreases, while in Ukraine conditions had worsened even more.
"The crisis has unsurprisingly had a much greater effect inUkraine, where violence has disrupted distribution chains andfrightened away foreign investors, including big advertisers,"it said. "We expect ad spend in Ukraine to fall 49 percent thisyear."
According to media reports, Interpublic Group's Magna Global also trimmed its forecasts for next year, takingits biggest cut to expectations for Russia.
(Reporting by Kate Holton; Editing by David Holmes and LouiseHeavens)