Thanks for your help.
Steve
I think it is the latter case - impressions are only counted when your ad is actually on a displayed page. Although I'm guessing that it would still be counted even if the user needed to scroll down to see it but didn't.
I don't know how you can distinuish between zero searches and zero impressions though.
Maybe the "magnifying glass" will give you a clue "e.g. your Ad is showing but is not on the first page"
Test a handful of keywords and see... sometimes, a search for the exact keyword phrase will show your ad for a broader keyword - explaining why the more detailed keyword didn't get any impressions.
It can be frustrating, especially when you're bidding on an Exact match keyword, yet a broadly-related Broad or Phrase Match keyword matches instead.
i have also noted that in competitive categories, like finance, impressions start showing up on popular terms only when really high bids are placed to compensate for newbie quality scores.
a few things you can do:
0. if you're getting no impressions, but a search on google for that keyword shows lots of ads, then increase your bid.
1. if you're getting no impressions and a search on the term yeilds no results on google, most likely there's no market for your search term.
2. check to see if you are geo-targeting. if applicable, national syndication will give you more impressions.
3. you may want to change the match type to broad to capture more queries. if you can, ex-post you can strip the query to find what term mapped to the broad matched ad that was shown.
hope that helps.