PPC ROI Forecast

[rbmito]

Hello
Was wondering which methods are often used and / or reccomended when forecasting ROI for a PPC campaign (or any other campaing).
We have been working on our campaign in the past 2 years and have monthly information since 2005.
Information includes:
- Impressions
- Clicks
- CTR
- Budget
- number of items sold (from the PPC campaign)
- monthly revenue
- ROI
For 2007, the only information I have is the monthly budget to be used in the campaign

I have been asked to forecast the total ROI for this year and after playing with the numbers, noticed that there are many variables (market trends, seasonallity, competition, keywords, creatives, etc) which will definitively affect my forecast.

Could someone let me know if there is some "standard" way for forecasting ROI?

Thanks!

[Fking]

you may also want to consider that even if your budged is twice bigger, this will not necessary increase the profit, because the engine may not have more traffic for your terms

[ClickingFast]

The biggest issue is that tracking ROI is hard because people can come to your web site and call or email you. You may never realize they found you initially in google unless:

- You create a contact form from your web site
- You ask people on that form how they found you
- You use google tracking code and google analytics to track these leads

Even if you do all of the above its still hard to track if someone comes to your web site and calls you. Best way to guage that is ask every prospect on the phone "how did you hear about us" That will help with PPC and across the board for marketing

Eric