Why does the EPC suddenly drop?

My friend's site has a conundrum...

[OptiRex]

A friend of mine has a nice business hobby site earning about $900 a month from Adsense.

Every now and then, maybe 2-3 times per month, his EPC is slashed in two, yesterday was one of those days. Today the EPC is back at "normal" levels.

I'm at a loss to explain just "why" this happens.

Is it an Adsense aberration, even going by 21_blue's averages' analysis it's a strange occurrence.

Does anyone else see this since my sites do not...yet!

[Moglex]

I haven't been here long, so this may have been mentioned already, but is it possible it is because you have a tightly focused site that was getting a lot of clicks for a particular advertiser, and that advertiser had a hiatus, causing less well paying ads to be displayed?

[21_blue]

Optirex wrote:

even going by 21_blue's averages' analysis it's a strange occurrence

This fits in with my averages analysis. In my Golden Gate [webmasterworld.com] post, I said: “occasionally, (a couple of days a month) your daily earnings will be unusually high or low”.

[OptiRex]

Moglex

I wish it were something so simple as that, I'm assuming it's not that since his site is great, good paying regular advertisers and well targeted ads.

As I said, it's only maybe two or three times a month, for instance today he's already earned more than the whole of yesterday and to all intents and purposes nothing looks any different whatsover except for the occasional diabolical EPC drop.

He takes it philosophically as "swings and roundabouts" however it bugs me since there seems to be no logic nor pattern to it except for the 50% reduction in EPC.

[hunderdown]

There has often been a thread here about the "stats being stuck." So we know that Google doesn't always report hourly on our stats.

I have a theory that they deliberately shift some of their reporting around to prevent publishers getting a fix on what clicks lead to what earnings.

On the days when your friend's earnings took a dive, maybe some clicks had been "moved" to another day?

[OptiRex]

I have a theory that they deliberately shift some of their reporting around to prevent publishers getting a fix on what clicks lead to what earnings.

If that were to be true then why do I not see that on my sites?

My friend has the theory that it's people/companies forgetting to keep up with their Adwords budget, highly unlikely but I suppose plausible.

“occasionally, (a couple of days a month) your daily earnings will be unusually high or low”.

This site fits your analysis perfectly 21_blue, 1st February an all-time high and 6th February the pits, today cruising nicely!

[Nitrous]

900 a month isnt really enough clicks or visitors daily to draw any conclusions from

I have 10 or 15 hobby sites that earn 5 times this much combined monthly. Together they are always within 10 percent total income for 2 years plus.

Individually they look extremely unstable with different single sites earning as much as all the rest combined at times and at other times only 5 dollars a day. Depends on so many factors that it isnt remotely predictable.

If I only HAD one site I would think that the EPC/CTR/ECPM varied wildly! And would try to figure out why. Together they are very very stable! You need about 3.5k to 4k monthly, a bunch of sites on different subjects to see this.

[FrostyMug]

it happens to me too. 2-3 times a month I'll have a 'really' low day. i usually attribute this to hiccups on AdSense server or new code release on their end. no biggie, it always comes back.

[leadegroot]

I see it too and have been attributing it to Advertiser Variance - for example, I have one particular advertiser that some evenings will increase their CPC 5 fold (yes, I love them :)) , and they will become the only ad in a wide skyscraper.
The topic of my site has a dual audience of buyers and sellers on the topic, and I assume this advertiser has a belief that the sellers, their market, is more likely to be on in the evening.
They aren't advertising at the moment and my ecpm is way down. I miss them so... ;)

[jomaxx]

I know you're far from an AdSense newbie, but I have to agree with Nitrous that at the $30-a-day level you have to expect a fair degree of volatility. I have one site that's in that general range and the eCPM normally varies within about a factor of 2.

I don't think it really requires an explanation. Just stuff happening.

[OptiRex]

Just stuff happening.

Ah, the answer to everything when we simply don't know:-)

I have one particular advertiser that some evenings will increase their CPC 5 fold (yes, I love them :))

Wow! I'd love to see their success rate statistical analysis. Have they ever tried it during the day to see what happens?

Since you're in Brisbane, is their site aimed at Oz since your evening would be the European start of day?

[leadegroot]

OptiRex:
Yes, its an Australian-targetted site and my favourite advertiser is also Australian-targetted.
(Havent seen them in a week or so, darn it...)
Wouldn't it be interesting to get an inside line on their conversion figures? :)

[dollarshort]

Its a very easy explanation, one of his high paying avdertisers with a high CTR dropped out for the day. Thats it. Try not to read too much into it.

[dollarshort]

Theres some looney theories on smart pricing circulating try not get caught up in them too.

[OptiRex]

Its a very easy explanation,

Hmmm...I prefer 21_blue's analysis, anything that's supposedly easy to explain usually has a flaw in it:-)

And the flaw would be, why would all the regular advertisers all do this on the same day meanwhile the balance 27-29 days of the month pay the regular EPC?

Sorry, I don't buy (sic) that one!

Stuff happens...I can accept that...

[21_blue]

Optirex wrote:

anything that's supposedly easy to explain usually has a flaw in it:-)

Which side of Occam's Razor was that written on? :-))