Sep 6, 2010 14:57 GMT  ·  By

A leaked document sheds some light on the top Google advertising spenders for the first half of the year. The document shows not only the big spenders, but also how much most companies are spending on search advertising.

There are only four companies spending more than $5 million per month on Google ads, as the numbers for June 2010 show.

Some of them are known to the public and somewhat to be expected, AT&T or Amazon, but Expedia, a travel site, and Apollo Group, a company owning several learning institutions, are a bit more surprising.

Note that the numbers cover just the US, as is obvious from the top names. Other big spenders are eBay, with over $4 million and Hotels.com and several others.

An interesting entry is BP which spent nearly $3.6 million on search advertising in June. In the months leading to the Gulf of Mexico oil spill, at one of BP's drilling sites, the company spent only $57,000 per month on Google ads.

Of course, considering the amount of bad publicity BP got over the spill, the ad spending doesn't look that surprising.

In total, there were just 47 advertisers that spent over $1 million in June. An additional 71 spent between $500,000 and $1 million. A further 357 spent over $100,000. Finaly, 1,356 advertisers spent between $10,000 and $100,000.

Added up, all of these customers spent $574 million on Google in June in the US alone. These are just direct-billed customers, the companies big enough to handle their advertising spending directly with Google.

However, Google makes a significant portion of its revenue from small companies using the self-serve tools provided by the search company. The top ten spenders in June only accounted for just 5 percent of Google's search advertising revenue in the US for that month.