Keyword QS: What determines the Minimum CPC?

Are there degrees for each type of Quality Score?

[netmeg]

This is something that I don't think I remember seeing addressed anywhere, and I'm kind of curious about it.

I'm wondering about Minimum CPC and Quality Score. Specifically, the Poor Quality Scores.

In looking over various accounts for myself and my clients, I see that even though a keyword has a QS of "Poor" the minimum bid can be as low as $.40; almost all the ones I see have minimum bids of $.40, $.50 or in rare cases, $1.00. I have *one* keyword (out of about 6500) with a minimum bid of $5.00. I've heard of minimum bids of $10.00, but never gotten one. So why the disparity? Are some Quality Scores poorer than others? Is it taking Account QS into the calculation?

Recently I had a keyword with a QS of "Poor" and a minimum bid of $1.00 suddenly drop down to a minimum bid of $.40. I hadn't done a thing to the landing page, ad group, match type, bid, or ad, and the QS was still "Poor" - so why the change? Was it suddenly a little more relevant but still not quite enough to slide over into "Ok"?

[tomasvdb]

from conversations with google employees i understand that the QS algorithm is constantly being revised (one even came close to calling it buggy at one stage) which would explain the erratic behaviour of the min CPC.

We've been analysing minCPC behaviour for various clients over the last 6 months, but there seems to be very little pattern or consistency mainly b/c parameters such as 'landing page' are hard to quantify.

Given the various comments i read from adwords users on the enigma that is the minCPC, i'd say the algorithm is still not stable...