In my SEO Best Practice guide I talked about the importance, particuarly in some consumer markets, of tracking through time your search volume to assess how much share of paid search or natural search you are achieving. Previously this was possible through tools such as the Google Traffic Estimator within the Adwords account, but only if you store historic data.

Now a new tool,Google trends, is available to help with this. Similar in look to the free blog monitoring tool Blogpulse it can show you:

• search volume
• for a specific keyphrase
• for a specific country
• through time
• compared to other keyphrases (separate by commas)

Unfortunately there is no scale, but it seems to be linear on volume. It does allow more precise phrase matching based on quotes. It doesn't show phrases less than a few hundred phrases per month.

Some interesting applications showing big volume changes through year.

• Compare retail, e.g. consumer electronics - compare mobile phones, ipod
• holidays, holiday spain, holiday cuba
• cheap holiday,cheap flights
• "cheap holidays", cheap holidays - showing relative few people qualify this phrase.
• Compare brands - barclays,hsbc,lloyds tsb,halifax

Generic phrases such as mobile phones seem to fall gradually through time, possibly because more sophisticated users are searching with more keyphrases.