What is the relationship between halved and half 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.

Prior to 2012, oil exports provided half the Iranian government's revenue and made up one-fifth of the country's GDP; its exports have been more than halved since.

Answer: product_or_material_produced