Utilize the input text as a context reference, choose the right relationship between tanked and video on demand 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.

US media shares tank Major media company share prices tanked by $50 billion there last week amid weak results and fears younger viewers and families are defecting from traditional linear, cable television to ad-free subscription video on demand (SVOD), compounding a weak advertising market.

Answer: distribution_format