Hi- I need some participation with this community to help me sample your opinions regarding something I will call AdWords Click to Sale Percentages.

If you would be so kind as to let me know what you think and what your logical answer would be, I would consider it a great favor.

Thanks!

Scenario
Lets say that you had click and sale data that spanned 8 quarters. In those 8 quarters the first 5 quarters had a PPC click to conversion rate of 1.56% with zero flux in that percentage month to month and quarter by quarter.

Then you noticed that the remaining 3 quarters had a click to conversion rate of 1.12% with zero flux in that percentage month to month and quarter by quarter.

In the time when all of this was occurring 3 major items happened.

1) A new shopping cart was implemented in quarter 6

2) PPC methodology remained consistent until it shifted in quarters 5 thru 6. After that it was reverted to the original methodology in quarters 7 and 8. Meaning we had a major change in methodology in the 5th and 6th quarters.

3) Some major web design changes were made in quarter 7 and remains today...

Of these 3 major changes what seems like the most likely culprit for a click to conversion rate decline of 28.21%?

Because i do not want to taint the results, I will keep my opinion to myself. Again, if you can please help me out by making a choice, I would consider it a great favor. I plan to take this data and throw the record counts in to a spreadsheet and present it as unbiased results.

Its always better to solicit from people who are not vested in the issue.

Thanks!