Know-How Exchange : Advertising/PR

Looking for any guidance or benchmarks around what an insurance carrier might expect in terms of sales lift if they make an investment in an advertising and direct marketing campaign. I know there are endless "it depends" variables, but just trying to gather some case studies or data points that can be interpreted and applied appropriately based on the relevance to this situation. Besides the eventual impact on sales, other metrics of interest include quote activity, cost per lead and close ratio. Thanks for any insight you can provide.