Answer

According to the U.S. Census, "the "Retail Trade" sector comprises establishments engaged in retailing merchandise, generally without transformation, and rendering services incidental to the sale of merchandise.  The retailing process is the final step in the distribution of merchandise; retailers are, therefore, organized to sell merchandise  to the general public".   

Go to the NYU Business Library's Economic and Statistics page for links to useful resources including the following suggested resources: 
Data-Planet Statistical Datasets: Provides current and historical datasets. To browse by subject. Select Industry, Business and Commerce then narrow your results by typing in Retail Trade and Food Services. 

Passport: Global research data including: market data & forecasts, economic indicators, and more. Type retailing in the search box to find market reports by country and industry. 

You may also want to consult the following sources:

U.S. Census Bureau collects retail trade data. 

National Retail Federation, the world's largest retail association .