How does Google determine which ads get shown?

If there are a hundred ads for a particular keyword or targetting subject

[DingoNY]

In some very competitive areas - the top PPC values can be quite high - then they begin to drop off rather quickly I think.

If you're displaying a banner - why doesn't each new visitor get the exact same (top 4 paying) adwords ads?

What is the logic by which they shuffle them around?

[Craig_F]

the relevancy to your pages is different. the top 4, as you put, only applies to keyword searches on Google itself.

[DingoNY]

I'm not so sure you answered my question :)

My site (particular page) is highly targetted about "blue widgets".

All of the ads on that page are about "blue widgets".

Some days my CPC fee of that particular page (channel) is $0.30 - while other days my avg is $0.10-$0.15.

I just don't understand why - because the content of my page is not changing - the ads are generally the same type of ads - I'm just seeing big swings in the CPC. Makes me curious as to how the serve up the ads.

[Jenstar]

It could be unrelated to your page, but is instead fluctuations on what the advertisers for those keywords are using for maximum bid prices and daily budgets.

Some advertisers turn off or downgrade campaigns over the weekend, when they can't keep as close an eye on it. Others might find highest conversions on the weekends, so will up their bids and budgets.

[fezziwig]

It's all part of the smoke and mirrors routine. By not discosing the clickthru costs, Google has the ability to work the numbers anyway they want.

Imagine betting on a roulette wheel where the odds changed at the whim of the house. :)

[DingoNY]

Jenstar - it isn't a weekend / weekday thing.

It is days of the week. Really bizzare.

I guess no one else has really noticed this?

[Jenstar]

>> Jenstar - it isn't a weekend / weekday thing.

The weekend/weekday is the most obvious example, but there are people who adjust their bids many times in a single day, which could be reflected by this.

[DingoNY]

Ok I just reloaded my stats.

In the last couple hours I had 2 clicks that essentially took my average up from the $0.10 I was mentioning before to the $0.30 that I am looking for. :)

So it seems - that either the total earnings are not updated with the click count... Or more likely (based off experience here) - I have some ads that run on my site that are paying more than $0.30 and it averages out.