eMarketer has trends and some data, such as CPC ("cost per click).  

According to Investopedia, a white paper is generally issued by a company but also a government agency.    

• A white paper promotes a certain product, service, or methodology to influence current and prospective customer or investor decisions.
• Three main types of white papers include backgrounders, numbered lists, and problem/solution white papers.
• A white paper provides persuasive and factual evidence that a particular offering is a superior product or method of solving a problem.
• White papers are commonly designed for business-to-business marketing purposes between a manufacturer and a wholesaler, or between a wholesaler and a retailer. 

Examples of white papers related to Social Media & marketing:

Hootsuite - software that helps communicate between social media channels and provides analytics.   The company produces a social media trends paper annually, which may include data. 

Accenture - consulting firm which publishes occasional papers on various topics.    They have papers on social media as commerce.