12 Questions to Define Market Size Like a Pro

Determining the market size for your product or service can be tricky. Answer these questions and you're well on your way to presenting your market size like a pro.

Questions

1. Define your target audience & target city. From publicly available census information (depending on the cities or towns), how many constitute your target audience?
2. Are revenues for major players decreasing or increasing? (Using publicly available data)
3. How much is your industry worth? (Review industry articles and note the smallest & largest your industry could be worth)
4. How much has your industry grown over the past decade?
5. What new developments are changing the size of your industry? 
6. Has distribution changed within your industry?
7. What are new trends and emerging channels for distribution?
8. How does your business utilize current and new prospective distribution channels?
9. What are major trends in your industry?
10. What are substitute products in your industry?
11. What are barriers to entry? 
12. In your industry, is it possible to achieve an economy of scale?

Links below for more info

USBA, U.S. Small Business Administration - Market Analysis
Wikipedia - Market Analysis
Entrepreneur - Conducting Market Analysis
Entrepreneur - How to Do Market Research
Inc.com - How to Write a Market Analysis