How do I find out which site is charging my credit card?

Economists define a "public good" as one which can be consumed or used by an unlimited number of people at no additional cost to the provider. Radio broadcasting produces a public good. A radio program is produced at a fixed cost, but an unlimited number of people within the reception area can receive that program. When one additional listener hears the program, no additional cost is incurred by the broadcaster for that listener. For this reason, sale of program advertising by broadcasters can produce income without excessive cost. If a listener hears a radio program, but does not respond to its advertising, no additional cost results. A listener who hears the radio program but does not purchase advertised products is a "free rider."