Investors will be eyeing Google (GOOG) today after the closing bell, as the online search specialist reports first quarter earnings. Analysts are expecting net income of $4.52 per share, 22.8% higher than the same period a year ago. Revenue is expected to come in at $3.61 billion, up 6.5% from the fourth quarter of 2007.

Most companies would kill for that sort of expansion given current economic conditions, but Google's growth clip is off significantly from previous levels. First quarter earnings in 2007 were a whopping 60.6% higher than 2006 numbers, which were almost twice that of 2005.

According to the company, Google generates 44% of its revenue from overseas. Investors should welcome this trend, as online growth rates begin to cool in the U.S. Abroad, however, Internet use is still expanding rapidly.

In recent months, much has been made about Google's relative susceptibility to the continuing economic slowdown. The company doesn't provide formal earnings guidance, and according to The Wall Street Journal analysts rely heavily on data compiled by ComScore, a compiler of online clicking habits. On Tuesday, ComScore reported that, compared to the fourth quarter of last year, first quarter clicks on Google search ads declined 9.3%.

Some investors fear Google has saturated its primary market -- online search --- and is now more exposed to oscillations in economic activity. Small and medium-sized businesses are already scaling back advertising campaigns, eating into Google's bottom line. CEO Eric Schmidt maintains his company's results aren't closely tied to greater economic strength or weakness. Meanwhile, skeptics accuse the company of failing to generate revenue from its forays into other markets, like online document sharing, email and word processing applications.

Google's challenge will be to find ways to grow during challenging economic times, especially if Microsoft (MSFT) ends up succeeding in its attempt to swallow Yahoo (YHOO). Google best gear up for a fight.