Our Head of Search, Polly Pospelova, has written a piece for State of Digital (.com) on how you can track competitors PPC spends.
"Businesses are always keen to know about their competitors marketing activities and how much they’re spending. I often come across blogs and forums where marketeers ask the same question: ‘Does anyone know of any sources for gathering paid search advertising spend for competitors?’ PPC spend on campaigns seems to be of particular interest.
There are tools that provide a variety of information but if you try to estimate your own campaigns and compare the estimates with the real information, you will find out that the results are completely inaccurate. The best you can get is a very ballpark range of spend, but nothing that can be used as a bulletproof source.”