If search impression share is under 100%, does it mean another company is bidding on our brand Keywords?
There is no information about any competition in the Adwords interface but the IS has gone down from 100% to 98% and it seems to be affecting the amount of conversions coming in. Is there anyway to get more detailed information than what I can see in the auction insight?
In short, IS is not a reflection of competition. Your IS is simply the ratio of searches that you could have shown for and the searches that you did show for.
So it is likely to be a budget issue. I suggest adding a few more columns, there is IS lost due to rank and IS lost due to budget.
The only way a competitor has an effect on your IS is indirectly, and having one competitor suddenly start to bid on your brand terms should (and in most cases will) not change your IS.
There is no way to get more detailed information regarding this on the AdWords platform though.
I suggest using the 2 columns mentioned above to see what they say, although I doubt they will tell you much in this particular case as you have only gone from 100% to 98%, this may not be enough data to tell you why (unless this is over thousands and thousands of impressions).
A 2% drop in IS is nothing to worry about at all. Give it a bit more time and identify a trend before you should start worrying, as said earlier it may simply be that your budget ran out one day and this means that there were a few searches for your brand term that you were not able to show for.
hope this helps
Re: Impression Share
A small addition to what has been said above, you could look at the Auction Insights Report (since you talked about what other companies are doing)and see where other advertisers are standing during the same ad auctions. What you can do is that you can go to Keywords Tab , click on Details >> Under Auction Insights either click on all or selected. That would give you an estimate of where you are in front of others and there are some important metrics which can be benchmarked and might help you with more optimization process.
More details around this report are here: https://support.google.com/adwords/answer/2579754?hl=en
Re: Impression Share
> Look at the search queries within the campaign in question and add terms that match theme of your campaign.
> Add negatives from search queries
This way you would be able to reshape what you would like to target. Since you already have and IS of 98% , you should not come across too many keywords and negatives to be added.