SAN FRANCISCO (AP) -- Google's earnings are still rising at an impressive clip even as a long-running slump in its ad prices deepens and management gambles on risky ventures such as its unprofitable purchase of smartphone maker Motorola Mobility.
The latest evidence of the company's moneymaking prowess emerged Thursday with the release of results covering the holiday shopping season and the advertising blitz it produces. Investors evidently liked what they saw because they drove up Google's stock by 4 percent in extended trading to position the shares to reach a new peak Friday.
Although the company's earnings rose 17 percent during the fourth quarter, there were further signs of deterioration in Google's ad prices despite efforts to close the gap between rates for mobile devices and for traditional computers.
Google's average ad price during the fourth quarter fell 11 percent from the previous year. That was the steepest quarterly drop in 2013. It marked the ninth consecutive quarter that Google's average ad rate, also known as "cost per click," has fallen from the previous year.
Online advertisers haven't been willing to pay as much to reach prospective customers on the smaller screens of smartphones and tablets.
However, Google has been tweaking its digital marketing system so mobile and PC ad campaigns are bundled together. In doing so, Google Inc. is hoping advertisers eventually will recognize the advantages of reaching people on the go and gradually begin to pay higher prices for mobile marketing pitches.
Mobile devices now generate nearly one-fourth of Google's total ad revenue, up from a small fraction just two years ago, based on estimates from the research firm eMarketer.
Google would have fared better if not for Motorola Mobility, which lost another $384 million during the final three months of last year. That means Motorola has lost more than $2 billion since Google Inc. bought it for $12.4 billion in May 2012.
Motorola's latest setback made investors even more relieved that Google won't be tied down by its subsidiary much longer, said Edward Jones analyst Josh Olson. Google announced late Wednesday that it's selling Motorola's smartphone business to Lenovo Group Ltd. for $2.9 billion in a deal expected to close later this year.
Analysts expect Google to eventually absorb a substantial charge to account for its Motorola misstep, though Google said nothing about it Thursday.
Google earned $3.4 billion, or $9.90 per share, in the October-December period. That compares with $2.9 billion, or $8.62 per share, in the prior year.
Excluding costs to cover employees' stock compensation, Google said it earned $12.01 per share. That was slightly below the average estimate of $12.22 per share among analysts polled by FactSet.
Revenue rose 17 percent to $16.9 billion.
After subtracting Google's ad commissions, revenue stood at $13.5 billion, in line with analyst projections.
Google's stock gained $46.71 to $1,182.10 in extended trading. The shares' high in regular trading stands at $1,167.89.
The stock's trading price is likely to be halved after Google executes a 2-for-1 stock split this spring. The company announced Thursday that the long-delayed split will be completed April 2.
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