People ask me periodically what my target market is. My answer is the same as most technical consultants: My target market is people who need my skills.
If you're a piano tuner, your target market is people who need their piano tuned. I'm a mathematician, so my target is companies that need math.
I may specialize in an industry some day, but so far what my clients have had in common is the nature of their problems, not their industry. They've come from legal, medical, manufacturing, etc. But they've all needed help with probability, numerical computing, etc.