What is the relationship between tanked and video on demand in the context of the input sentence. Choose an answer from: 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