Census data is often a good source of industry information. Use the NAICS/SIC codes to locate information such as establishments, employees, shipments and sales.
Using the "bakery/cafe" concept, here are some potentially relevant NAICS codes...
NAICS and /or SIC codes can be used in many business databases to help focus your search. Databases that allow searching by industry codes include
When you find a good trade magazine, browse through recent issues for marketing information.
Use Google Advanced Search to locate trade associations and reports. Limit your search to the .org domain. Good search terms include , data, statistics, trends.
Check out the trade orgnaizations webpages for industry and demographic data.
The best way to identify trade publications is through searching for your topic in the business article databases and then filtering by "trade publications. You can also search the Journals and Periodicals available from the Cheng Library by a simple term such as "restaurant".
Keep in mind that other industries might apply.