Okay, so run a campaigns with members report in SFDC. Set the parameters for the programs you want to analyze. There's a sample of some things you might filter for in the screenshot below. Make it a summary report and summarize by Lead/Contact ID. Now the report will show you, by lead, what programs/campaigns they are in that meet your criteria.
Next, create a formula field. In this example I've called it "Number of Email Responses." Make this field equal to the row count. Now you have the number of campaigns/programs by lead. I've chosen to hide the details in this screenshot, but if they were expanded you'd see the specific campaign names to which they responded.
This information at-a-glance will probably answer your question, but you could also calculate the average number of responses per lead. Export the
printable view to Excel. Divide the number of total responses by the number of rows (leads).