Utilize the input text as a context reference, choose the right relationship between Stock market and stock exchange from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Stock market officials and historians calculate that the Athens stock exchange has been forced to cease trading for at least a day on 14 other occasions since the bourse was founded and started trading in 1876.

Answer: operator