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(Pocket-lint) - Everybody knows Google makes a lot of money on advertising, but it begs the question: has Google become too dependent on that business model?

The company continually struggles to pull revenues from other sources, as evident by its fourth-quarter results that show more than ever how it is reliant on advertising against search results.

According to the latest figures released by the company, for the 90-day period ending in December, Google made roughly 89 per cent of its total revenue from advertising-related things, even though the company has invested time, effort, and billions into other projects ranging from Android to moonshot projects like robots.

Although revenue for the quarter was $18.1 billion, up from $16.86 billion in the year-ago quarter, and net income was up too, with $4.76 billion in profits compared to $3.38 billion a year earlier, Google's advert revenue has come under pressure as it continues to maintain the status of being the sole bread-winner for the company.

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Patrick Pichette, chief financial officer, admitted during Google's conference call that the company had "a few real challenges" in the fourth quarter, but he still hailed the strength of its core search business. That might not be enough to appease investors though, who could question Larry Page's, Google's CEO, handling of things.

He's even had a hard time achieving significant gains apart from Google's search and advertising business for desktops, for instance. More consumers are getting online through mobile devices like phones and tablets, but Google said the average price of its online ads fell 3 percent year-over-year during the fourth quarter.

Google is making less money from mobile ads, and according to eMarketer, its share of the mobile market is shrinking.

That stark contrast in reality versus headline-grabbing products like Android Wear and Glass prove that - even though Google wants to be known for things beyond "adverts against key words" - the company's key revenue still lies in online advertising via desktops, and that business - that core - is slowing.

It's not all bad news, though. Positive takeaways from the earnings suggested that Chromecast is a hit, with a 60 per cent increase in usage since its launch. Chromebooks are supposedly enjoying some success in school too. Neither, however, were enough to move the needle.

Tune into Google’s live call at 1:30 PM PT to hear executives discuss more details about the earnings release.

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Writing by Elyse Betters. Originally published on 29 January 2015.