If you use Google for measuring competition levels for keyword phrases, you probably use the intitle and inanchor searches to give you some data. But I've noticed that the results returned by Google can change quite dramatically from one day to the next. Having kept spreadsheets full of this data for a few clients and their keywords, I've noticed that if I try the same searches (inanchor and intitle) on another day, I'll get very different numbers (sometimes huge differences). I realise that hundred of thousands of page are being added to the Google index every day, so the raw number of results for a keyword search are likely to change every day, but I didn't expect this much variation in the advanced searches. Makes it very difficult to conduct proper keyword competition work when the goalposts are continually moving
Welcome to ever-flux.. they are doing data refreshes more frequently these days at G... As well as pages added, ONE Spammer that get's banned could have some 100k pages... some many variables huh? That's the fun of it
I do use inventory overture for checking demand of a particular keyword. For competetion and supply I search for the term in specific SE with and without quotes. Say you are doing keyword analysis for the keyphrase Used Cars. Inventory overture will give the count or demand of this keyphrase in the search market. Search for "Used Cars" it will give the competition data. As this will give the search result of those sites which exactly use this keyphrases. Without quote will give you a result of those sites which consists either of the words. So you can get the supply idea.
Google has a nice tool (https://adwords.google.com/select/KeywordToolExternal). Shows how many people search for a term and how much competition there is for it.
Another thing I should add to this is that one SEO book I read was instructing about using your google toolbar to check the competition for a keyword...well take the toolbar PR with a grain of salt because it may not always be telling the truth...
I use BlogMaster's Keyword Finder. It gives you keyphrases from Yahoo! Keyword Selector Tool (Overture) with projected yearly results, monthly searches, weekly, dayly and hourly average searches plus number of competing sites on Google for that keyword phrase (with quotes).
I tried to look up one of my longtail keywords and the character limit for the search box is too low. Lame.
the point of keywords are that most of the results are not showing reality because many webmasters do reasearch on the keywords and they hit them and by the way overture I think always shows higher number of searches just because they could attract more bidders..