BPA Worldwide is a US-based company that provides independent, third-party audits of audience claims of business-to-business and consumer media and events. Its membership includes magaziness, newspapers, web sites, events, email newsletters, digital magazines and other advertiser-supported media produced by its members. The company is a not-for-profit, (501(c)(6) organization, and is one of the largest auditor of media in the world in terms of membership, which consists of media owners, marketer companies and advertising agencies. In addition to its US headquarters, BPA operates offices in Canada, UK and China.