Look out fishwraps: A new study by the Interactive Advertising Bureau and PricewaterhouseCoopers found that U.S. Internet advertising grew 38% in the first quarter to a record $3.9 billion. And you know what that means, right? Our future rests withGoogle (NASDAQ:GOOG).

Or does it? Google certainly is hugely influential, but I expected more when I ran the numbers. It turns out that the heavy in search probably earned a still-impressive but hardly earth-shattering 22% of total domestic ad revenue in Q1.

Here's how the math works. According to Google's most recent 10-Q, 58% of its advertising revenue originated in the U.S. during the first quarter. No explicit numbers are given, but multiplying Google's reported $2.23 billion in ad revenue by .58 equals $1.29 billion. Using the same formula for Google's traffic acquisition costs reduces its total applicable TAC to $419 million. Subtracting the two ($1.29 billion-$419 million) leaves $872 million in Q1 U.S. ad revenue, or 22% of $3.9 billion.

That's not to say Google isn't doing well. Consider Q4, for example. Google says in its 10-K that 62% of its revenue originated in the U.S. during the fourth quarter. Run the same math equations, and you find that the company probably booked $786 million in total U.S. ad revenue after traffic acquisition costs, good enough for 21.8% of the $3.6 billion pool tracked by IAB and PricewaterhouseCoopers in Q4.

In other words, Google is climbing higher on the Web advertising ladder, but, so far, it's able to take only one rung at a time.

For investors, the IAB-PwC report offers what may be the best vehicle yet for understanding the raw might of Google. Sure, it's impressive, but is it really all that? Frankly, I had expected Google's share to be somewhere north of 40%, considering its valuation. Obviously it's not, but that's not even the worst part of the story. Google's competitors are doing pretty well. Take Yahoo! (NASDAQ:YHOO), for example. Using the same equations on the data found in its most recent 10-Q shows it to have an estimated 16% of the U.S. online ad market in Q1. Not too shabby, eh?

All of this has me wondering: As great as Google is and may still be, the evidence doesn't support the king-of-the-online-world valuation that the stock sports today. That may change, of course. Just don't expect it to happen soon.

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Fool contributor Tim Beyers hasn't read the newspaper classifieds in ages. Turns out he isn't the only one. Tim didn't own shares in any of the companies mentioned in this story at the time of publication. You can find out which stocks he owns by checking Tim's Fool profile . The Motley Fool has an ironclad disclosure policy .