Google Inc. (GOOG) likely will report more gains in search-advertising revenue and market share when it reports fourth-quarter earnings Thursday, according to technology researcher IHS iSuppli Corp.

Based on results for the first three quarters of the year, the group estimated Google's full-year search advertising revenue last year rose 20% to $25.4 billion, while its share of the search market widened two percentage points to 83%.

Vincent Letang, an analyst for IHS, said the arrival of Microsoft Corp.'s (MSFT) Bing search engine and increasing competition in growing markets like China, Russia and South Korea both indicated 2010 "might be the year that Google would surrender some of its dominance in the global search advertising market." But despite those headwinds, Google still outgrew the overall market, he said.

The global search advertising market grew 17% percent from 2009, which was marked by a slowdown that year, IHS said.

The group also estimated that display revenue increased 61% last year. Google for the first time provided revenue data for both its mobile unit and display advertising business in its previous earnings report.

Investors have been worried about a possible slowing in the pace of growth in Google's core search advertising business, which generates most of its total revenue.

Google shares were up 0.5% at $642.75 in after-hours trading.

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