In their Friday blog, Google announced they have launched a new feature in the AdWords interface, Impression Share - the percentage of impressions your ads see. Thus giving very accurate numbers for total searches for all keywords or their expanded matches.
The feature is well detailed by the Googlers.
The Original Search Marketing Event is Back!
SES Denver (Oct 16) offers an intense day of learning all the critical aspects of search engine optimization (SEO) and paid search advertising (PPC). The mission of SES remains the same as it did from the start - to help you master being found on search engines. Register today!