PPC Defense: Don't Let These 7 Factors Damage Your Performance
Set performance thresholds. Establish a baseline for your performance and when you fall below a certain watermark, and then it's time to take stock of your stable of competitors. You should keep an eye on click-through rate (CTR), cost-per-click (CPC), impression share, and impression share lost due to ranking (IS lost due to budget doesn't necessarily indicate an increase in competition). Utilize a third party competitive tool. There are a handful of third-party tools that help monitor competitor behavior. To be diplomatic, I won't mention any specific tools here, but if you search for "PPC competitive tool," you'll get a whole SERP full of available options. If you want to monitor your competitive landscape, then you should compare the available tools and select the one that best suits your needs.