You’ve accepted that “the general public” is not a target audience. Congratulations! Now’s the fun part: learning more about the groups of people who really are most important to your success.
You can and should do some original research via surveys, interviews, and informal focus groups with people on your lists (which I talk about in Chapter 3 of my book). But you can also learn a great deal from polls and surveys conducted by others.
Check these sources for free data you can use to better understand your target audiences.
Cornell Universities List of Public Opinion Surveys