Completing the business plan is the biggest hurdle for most people who want to start a business. I hope I'm not alone, but it is truly one of the most daunting documents that I've ever had to work on - I'm still not done with mine. There's just something about writing a document where you need to project sales without having specific historical data, how am I supposed to know how many times Mary is going to go shopping in my shop? AND if it's not supposed to be a perfect projection then why do it in the first place? I know, I know - it's proof of concept and a necessary evil - but still!
So as you prepare to peer into the crystal ball, here are a couple of links to help with statistical data that you'll need for both demographics (target market) and for specific industry analysis.
shop.org (US internet usage, online shopper stats)
census.gov (demographics and industry stats, zip code-specific data available)
United States Department of Labor (average wage statistics - can be helpful when determining target market numbers)