Google Insights for Search is another great tool that can help marketers plan and refine their campaigns. It lets you compare search volume patterns by category and geography over time. You can explore seasonality, geographic, and product trends. As an example, by analyzing geographic trends over time of search patterns for your brand and your category, you might identify a high ROI metropolitan area to focus a concerted marketing effort.
There have been a number of studies that show that online display advertising has a multiplicative effect on conversion rates of sponsored search listings - as high as 22% improvement. (See Microsoft Advertising Institute.) But it's still hard to tell exactly how much impact your specific display ads have on your specific search campaigns.