Has anyone done or know of any empirical data on the average percentage of leads generated via phone call versus online form on a landing page. I know it can vary from business type to business type. More specifically I'm interested in the professional business services industry such as Engineering, Surveying, Commercial Real Estate, Accounting, etc.
So for example if you conversion rate for online form submission on a landing page is 3%, what would be a ballpark estimate for the actual conversion rate including phone calls? 25% more? 50% more? Double. "Ballpark" is the keyword here.